1) Abolish 2) Annul 3) Avoid 4) Cancel 5) Cancel out 6) Declare invalid 7) Discredit 8) Make invalid for use 9) Nullify 10) Quash 11) Reverse 12) Show to be invalid 13) Strike down 14) To render invalid 15) Void 1) Abrogate 2) Annul 3) Avoid 4) Cancel 5) Destroy 6) Disprove 7) Negate 8) Nix 9) Null 10) Nullify 11) Overturn 12) Quash 13) Refute 14) Rescind 15) Stet 16) Undo 
• (v. t.) To render invalid; to weaken or lessen the force of; to destroy the authority of; to render of no force or effect; to overthrow; as, to invalidate an agreement or argument.
to weaken or make valueless : to discredit.
To weaken or make valueless: to discredit. ... (18 Nov 1997) ... 
In·val'i·date transitive verb [ imperfect & past participle Invalidated ; present participle & verbal noun Invalidating .] [ From Invalid null.] To render invalid; to weaken or lessen the force of; to destroy the authority of; to ...
[v] - declare invalid 2. [v] - show to be invalid 3. [v] - take away the legal force of or render ineffective
invalidate To make invalid or to nullify.
verb make invalid for use; `cancel cheques or tickets`void verb take away the legal force of or render ineffective; `invalidate a contract`
to render invalid; discredit. · to deprive of legal force or efficacy; nullify.