Cold call

The word "cold" is the key part: it means you're calling a raise while entering the action with no chips voluntarily invested this round. If someone raises and you call without having limped, bet, or raised yourself yet, that's a cold call, even if it's just a single opening raise you're calling. The contrast is with a player who already put a bet in earlier that round and then calls a later raise; that's just calling the raise, not cold-calling.

It comes up a lot when there's been a raise and a re-raise ahead of you. If someone opens, another player 3-bets, and you call that 3-bet cold, you've cold-called the 3-bet. But the same label applies to calling one raise from the button or the blinds when you've put nothing voluntary in so far that round.

For beginners, cold-calling is often riskier than it looks, because you're committing chips against a hand that has already shown strength by raising, and you're doing it without the information of having acted first. A common habit is to lean toward folding or re-raising (a 3-bet) with strong holdings rather than flat cold-calling, since calling invites other players in behind you and gives up the chance to win the pot right away. It's a fine tool, just one worth using with a clear plan.