Reform is a process in which a government or other entity is changed, usually for the better.
In the mirror universe, Spock preached reform of the Terran Empire. Shortly after, Spock become Commander-in-Chief of the Empire and instituted his reforms. Unfortunately, these peaceful reforms resulted in the fall of the Empire. (DS9: "Crossover")
In the middle of the 2370s, Grand Nagus Zek, with help from Ishka, began to institute several reforms of the Ferengi Alliance. These reforms included the introduction of tax, the necessity of "receipts" for bribes and the introduction of social programs such as wage subsidies for the poor, retirement benefits for the aged and healthcare programs. The Nagus also created the Congress of Economic Advisors. Other reforms made waste dumping illegal and equal rights for all. (DS9: "The Dogs of War")