Equalises meaning : To make equal; to cause to correspond in amount or degree. To be equal to; to equal, to rival. To make the scoreline equal by scoring points. (underwater diving) To clear the ears to balance the pressure in the middle ear with the outside pressure by letting air enter along the Eustachian tubes. Said of a morphism: to pre-compose with each of a parallel pair of morphisms so as to yield the same composite morphism.