What "countergambit" means in chess

A countergambit is a chess opening in which a player, facing a gambit (a sacrifice of a pawn or a piece for an advantage in position or initiative), responds with a gambit of their own. The purpose of a countergambit is to seize the initiative and disrupt the opponent's plans. Examples of countergambits include the Falkbeer Countergambit in the King's Gambit and the Albin Countergambit in the Queen's Gambit.