The post describes the different understandings of what reform means: positive meaning of reform; radical or revolutionary critique of reform; revolutionary reforms or non-reform reforms; right-wing counter-reforms; and religious reform.
Dictionary definitions of reform include to “make changes in (something, typically a social, political, or economic institution or practise) in order to improve it.” and “a change for the better as a result of correcting abuses”
Positive meaning of reform
The most common understanding is that reforms result in changes in society to make it better for ordinary people. Not for the capitalists, the rich, business and property owners.
In Key Concepts in Politics and International Relations, Andrew Heywood describes reform as:
“to create a new form of something, to make it anew. The term ‘reform’ nevertheless always carries positive overtones, implying betterment or improvement. Strictly speaking, therefore, it is contradictory to condemn or criticize what is acknowledged to be a reform. However, reform denotes improvement of a particular kind, in at least two senses. First, reform indicates changes within a person, institution or system that may remove their undesirable qualities, but do not alter their fundamental character: in essence, they remain the same person, institution and system. Reform thus endorses change while maintaining continuity. Second, the change that reform stands for tends to have piecemeal character: it advances bit by bit, rather than through a sudden or dramatic upheaval. As a longer-term and gradual process of change, reform differs markedly from revolution.” 
Radical or revolutionary critique of reform
Some on the radical left argue that reforms are used to protect or maintain capitalism by making it more stable or profitable by defeating and limiting working-class struggle. 
There are also those on the Vanguard left (Trotskyist, Marxist-Leninist, Stalinist) that argue against reformism because capitalism can’t be reformed and so is a distraction from organising a vanguard party to lead the working class to victory over the capitalists : “reformist methods and revolutionary methods are not different paths to the same goal, but paths to different goals” 
Revolutionary reforms or non-reform reforms
These are reforms to make the conditions in society more open to revolution or to move society in a revolutionary direction: “challenge existing power relations and pave the way for more revolutionary changes in the larger society necessary for a more socially just and environmentally sustainable world.”  Their aim is not to reform capitalism – reformism. The idea likely originated from Leon Trotsky’s ‘Transition Program’ . This is also known as a ‘transitional demand‘ to link the current situation to moving towards a socialist society. The Trotskyist Committee for a Workers’ International describe transition demands as “Socialists fight for immediate reforms (minimal demands) but the day-to-day problems, unemployment, low pay etc. are linked to the socialist transformation of society by a series of intermediate demands (transitional demands).” They give recent examples of transition demands including reducing public spending cuts or increasing funding for the NHS .
André Gorz in his 1964 book Strategy for Labor compares ‘revolutionary reforms’ or ‘non-reformist reforms’ to ‘reformist reforms’ . Ralph Miliband called revolutionary reforms ‘structural reforms’ and understood that radically motivated socialist reforms would bump up against limits. Also that reforms would not take us on a path from capitalism today to socialism in the future without a rupture or revolutionary moment that was in no way a reform. 
Kier Milburn describes a similar concept, calling it ‘Directional Demands’:
“Directional demands aim to provide a direction of travel rather than simply describe the wish for ‘full communism.’ They need to make sense within existing conditions while pointing beyond them. Indeed they need to make better sense of the current situation and the potential it holds than conventional politics does. They need to play a compositional role, I.E. link different sectors or interests together or indeed produce a new subject of their own. And their fulfillment, or indeed movement towards their fulfillment needs to leave us, the working class, the multitude or whatever, in a stronger position, able to better articulate what we want and better able to exercise the power to get there. The Universal Basic Income (if framed correctly) could provide one example, a Debt Jubilee or Universal Expropriation (a residency restriction on housing), could provide others.” 
These are the neoliberal free-market policies of the Tory party and the right-wing of the Labour Party. The capitalists argue that the system can no longer afford progressive reforms because economic growth as declined compared to the post-war boom . The hard-right solution is to remove all employment protections so ‘Britain can compete globally’ . Also the continuation of the Tory privatisation project, specifically the NHS and drug prices at the moment.
The right (capitalists, elite, Tory party) commonly use the word reform when they are rolling back gains from the past. They know they can’t openly replace Britain’s health care system from the government-funded NHS to a private system like in the US without a huge public backlash. So they ‘reform’ (counter-reform) it with legislation such as the Health and Social Care Act 2012, which has introduced ‘competition and choice’. Brexit will likely mean an increase in drug prices. If we look at the history of the NHS, when the NHS was created in 1948, prescriptions and dentist visits were free. The Tories introduced dentist charges in 1951 and prescription changes were introduced in 1952. This is just one example of the many ways that the Tories roll back, dismantle and privatise the gains that ordinary people have won through struggle.
Religious reforms take place when a religious community decides that it has deviated from the ‘true faith’. Religious reforms will start in one part of a religious community and then spread, meeting resistance from other parts of the same religious community. Religious reforms result in a reformulation of the religious teachings viewed as ‘true’ and a rejection of the teaching seen as ‘wrong’. 
- Key Concepts in Politics and International Relations, Andrew Heywood, 2015 page 190
- (http://libcom.org/blog/reform-possible-reformism-guaranteed-22122011 and by endnote 35 https://libcom.org/history/revolution-back-agenda-mark-kosman)
- (https://iwpchi.wordpress.com/tag/reformism/, https://socialistrevolution.org/david-harvey-against-revolution-the-bankruptcy-of-academic-marxism/, https://litci.org/en/marx-and-the-impossibility-to-reform-capitalist-society/)
- https://data.worldbank.org/indicator/NY.GDP.MKTP.KD.ZG and A Brief History of Neoliberalism, David Harvey, 2007, page 154