When no one has yet Openeded the betting round, one may Check, which is equivalent to calling the current bet of zero.
The second and subsequent calls of a particular bet amount are sometimes called overcalls. That is, if one player bets, a second player calls, and a third player calls that same amount, this last call (and subsequent ones) are overcalls.
In a Fixed limit or Spread limit game, the act of calling a bet that includes two or more raises is called a cold call. For example, if the first player opens, and a second player raises, any player with no money already in the pot must call that full amount, and is said to cold call the two bets.
In public card rooms and casinos where verbal declarations in turn (and sometimes even out of turn) are binding, the word "call" is such a declaration. In particular, the practice commonly seen in poker games on television and in moives of saying "I call, and raise $100" is considered a string Raise and is not allowed in a serious poker game. Saying "I call" commits you to the action of calling, and only calling.