Nullify, v. t. [imp. & p. p. Nullified; p. pr. & vb. n. Nullifying.]
Etymology: [L. nullificare; nullus none + -ficare (in comp.) to make. See Null, a., and -fy.]
To make void; to render invalid; to deprive of legal force or efficacy. Such correspondence would at once nullify the conditions of the probationary system. I. Taylor.
Syn. -- To abrogate; revoke; annul; repeal; invalidate; cancel. See Abolish.
Shades of meaning
Fernald has no entry of its own for nullify; he lists it under abolish, cancel.
Where he writes about it:
There we use repeal, abrogate, nullify, etc.: repeal by the enacting body, nullify by revolutionary proceedings; a later statute abrogates, without formally repealing, any earlier law with which it conflicts. — from abolish