To deregulate is to take away some of the government's rules that tell a kind of business what it may and may not do. Airlines, banks, energy firms, and phone companies are the usual stories: a government that used to set prices or block new firms steps back, and the market is supposed to decide more for itself. News, law, and politics use the word a lot; it is not a kitchen-table word. People who like it say it means more choice and lower prices. People who do not like it say it means less safety and more mess later. The word itself does not pick a side — the speaker does. Though actually, deregulating is not the same as selling a government company to private owners, and it is not the same as having no law at all. It is a change of degree: fewer controls, not always zero. The opposite move is to regulate, or to put rules back.