WordNet sense 1 (the state of nonexistence):

nothingness, nullity, nihility

WordNet sense 2 (an empty area or space):

emptiness, vacancy, vacuum

WordNet sense 3 (lacking any legal or binding force):

null

WordNet sense 4 (having no cogency or legal force):

invalid, invalid

WordNet sense 5 (declare invalid):

annul, avoid, invalidate, nullify, quash

WordNet sense 6 (holding or containing nothing):

empty

WordNet sense 7 (take away the legal force of or render ineffective):

vitiate

WordNet sense 8 (excrete or discharge from the body):

evacuate