1.
negation; denial; contradiction
The act of negating or denying something. In grammar, refers to negative forms of words.
2.
cancellation; nullification; undoing
The act of cancelling out or nullifying an effect, action, or statement.
Derived from the verb 打ち消す (to negate, to deny). Very commonly encountered in Japanese grammar studies, where 打ち消し refers to negative forms and constructions.