Nit
An extremely tight player who only puts money in with premium hands.
A nit plays a tiny fraction of hands — often under 10% — and usually raises only the very top of that range. Online you'd call it a VPIP in single digits; live, it's the regular who's folded for forty minutes and whose raise makes the whole table sit up. Nits aren't cowards; they've simply concluded, often correctly, that most pots aren't worth fighting for.
The counter is twofold. First, steal from them: a nit defends so rarely that raising their blinds and c-betting small is close to printing. Second — and this is where most players bleed money — never pay them off. When the nit who's played two hands all night check-raises the river at $1/$2, they have the nuts or near enough. Your two pair is a fold. Calling a nit's aggression with anything but a monster is one of the most reliably losing plays in low-stakes poker.
Example: a nit opens to $10 from early position. Their range is something like QQ+ and AK — call it 2% of hands. Your pocket jacks are roughly a 2-to-1 underdog against that range (about 36% equity), and you're out of position. Even getting a decent price, this is a fold that feels wrong and is right.
At home games nits survive for years because nobody attacks them and everybody pays them off "just this once". If that's your table, be the one who folds to their raises and steals everything else. And if your own numbers show you're the one playing 9% of hands, the leak is yours — loosen up in position, and let the TAG and LAG entries show you the next steps. Everyone else should treat the nit as free money: their blinds are yours, and their raises are information.