The other definitions provided here aren’t exactly complete.

Tankie is a pejorative referring to authoritorian communists, specifically those who support one-party Marxist–Leninist socialist republics. It was originally coined to refer to those who defended the Soviet suppression of the 1956 Hungarian Revolution and the 1968 Invasion of Czechoslovakia, both of which involved the liberal use of, you guessed it, tanks. Over time, it has grown to encompass authoritarian leftists that support anti-western nations, e.g., Russia, China, and North Korea.

There has been increased semantic drift as, much like woke is used by the right, tankie has started to mean “leftist I don’t like” in some circles.

Leftists/Socialists/Communists that support or are apologists imperialist regimes simply because they also claim to be Socialist/Communist. The term specifically alludes to the history of some such regimes “rolling our tanks” on their own citizens, E.G. the Tiannamen Square massacre.

Tankies are folks who follow ideologies such as stalinism or stalinist-adjacent ones (e.g. trotskyism, maoism).

Here “libshits” takes most of the scale, because I’ve been called that a bunch of times, despite certainly not being a liberal or even in the center or right wing, and I’m kinda salty.