Suddenly, I find that tons of posts on /b/ are inappropriately using the word "cuck."

Cuck is a slang word that is just a shortening of the word "cuckold." This merely means "the husband of an adulteress."

You are using the word incorrectly or out of context. You either don't know what the word means are are just choosing to use the wrong word. Either way, you and everyone else that has been doing this lately are fucking retards.