First Day Communist Kid - a person new to to communism, marxism, marxism-leninism or marxism-leninism-maoism, who nevertheless thinks they know it all, even when facing actual communists telling them they are wrong.

This doesn't refer to them having a particular political position, just a lack of knowledge of even the sectarian positions they claim to have.

For example, a FDCK could lack knowledge of the Sino-Soviet split's importance or think that Scandinavia is market socialism.

A person with an outwardly dominant, masculine, or aggressive personality, but who also enthusiastically takes on the submissive or "bottom" role in the bedroom.

An intentional misspelling of the word fuck where the writer/speaker should have put u on top of the d.