nullify
nul.li.fy \'n*l-*-.fi-\ vt [LL nullificare, fr. L nullus] 1: to make null; specif : ANNUL 2: to make of no value or consequence ATE mean to deprive of effective or continued existence. NULLIFY implies counteracting completely the force, effectiveness, or value of something; NEGATE implies the destruction or canceling out of each of two things by the other; ANNUL suggests making ineffective or nonexistent often by legal or official action; ABROGATE is like ANNUL but more definitely implies a legal or official purposeful act; INVALIDATE implies making something powerless or unacceptable by declaration of its logical or moral or legal unsoundness SYN syn NULLIFY, NEGATE, ANNUL, ABROGATE, INVALID
Webster's English Dictionary