Tankie is a pejorative label generally applied to authoritarian communists, especially those who support acts of repression by such regimes or their allies. More specifically, the term has been applied to those who express support for one-party Marxist–Leninist socialist republics, whether contemporary or historical. It is commonly used by anti-authoritarian leftists, including anarchists, libertarian socialists, left communists, democratic socialists, and reformists to criticise Leninism, although the term has seen increasing use by liberal and right‐wing factions as well.

In layman terms, these are the people thay will have no second thought about enforcing communism at a barrel of a tank, which is the reference to how USSR had to invade Warsaw pact allies to suppress democratic liberalization efforts.

Think Hungary and Czechoslovakia