I asked this question a little while ago because I’ve heard the term but it’s not always clear what it is referring to. I think that similarly to ‘woke’ it is used in the context of ideological or political battles, so the definition is variable depending on the context. Opponents will likely have the widest definition since that way they can insult the largest group of people whose beliefs they disagree with, eg. “If you support Ukraine you’re a tankie”.
Words like ‘progressive’, ‘socialist’, ‘authoritarian’ are more appropriately descriptive if that’s what you’re going for. If you want to have an argument then ‘woke’, ‘tankie’, ‘SJW’, ‘karen/keith’, ‘snowflake’, ‘bootlicker’, ‘edgelord’, ‘redditor’ are good choices.