A tankie is someone who supports the CCP or unironically supports the USSR/Russia. They're generally authoritarian leftists. The term tankie comes from the tanks used to crush people at Tianamen Square
actually it came from when the USSR sent tanks to Hungary to keep down a workets revolution against the Soviet backed regime in the mid-twentieth century. Origanally it was used as a description for divisions in the British communist party between those who felt a global [Soviet backed] communist plan, versus those who supported independent worker collectives democratically deciding their own direction.