To call is to match a bet or a raise. A betting round ends when all active players have bet an equal amount or no opponents call a player's bet or raise. If no opponents call a player's bet or raise, the player wins the pot.
The second and subsequent calls of a particular bet amount are sometimes called overcalls. This term is also sometimes used to describe a call made by a player who has put money in the pot for this round already. A player calling a raise before he or she has invested money in the pot in that round is cold calling. For example, if in a betting round, Alice bets, Bob raises, and Carol calls, Carol "calls two bets cold". A player calling instead of raising with a strong hand is smooth calling, a form of slow play.
calling when a player thinks he does not have the best hand is called a crying call.
In public card rooms and casinos where verbal declarations are binding, the word "call" is such a declaration. In public cardrooms, the practice of saying "I call, and raise $100" is considered a string raise and is not allowed. Saying "I call" commits the player to the action of calling, and only calling.
Note that the verb "see" can often be used instead of "call": "Bob saw Carol's bet", although the latter can also be used with the bettor as the object: "I'll see you" means 'I will call your bet'. However, terms such as "overseeing" and "cold seeing" are not valid.