It isn't the best word, John knows, but it's the only one he knows to describe what he is. Other than perhaps Molly, which strikes a certain image in his mind that he feels is perhaps even more derogatory than the one that Jim is protesting as it stands.

He raises his eyebrows slightly as Jim continues -- pretty sure I've slept with more men than you.

"Is that a boast, Captain?" John tosses back, unable to help himself. "Or have I perhaps given you reason to suspect that my own sexual exploits are so limited?"