Annul, abrogate, void, vacate and quash are used chiefly in legal context and mean to deprive of validity, force, or authority. Though varying little in denotation, these words are not always interchangeable, their appropriate selection being dependent on the character or status of the invalidating agent and on the character of the thing invalidated.
Annul is the most general term, applicable to something (as a right, marriage, charter, or statute) that may be adjudged invalid or void. It implies the exercise of competent legal authority.
- had parliament, immediately after the emanation of this charter . . . annulled the instrument . . . the perfidy of the transaction would have been universally acknowledged
—John Marshall
To abrogate is the act of one having force and authority, and often legal jurisdiction. A ruler or an arbiter as well as a court may abrogate something (as a law, a treaty, or a convention) previously effective and in effect or in intent abolish it.
- we are not . . . called upon to abrogate the standards of values that are fixed, not by you and not by me, but by . . . time
—Lowes
Void in legal context retains much of its basic meaning, to make empty or null. It is often interchangeable with annul.
- the state supreme bench . . . voided the referendum
—A swell & Michelson
Unlike the latter it need not imply the action of a legally competent authority.
- it is the insanity of the testator that voids his will, not the act of a court
Only competent legal authority can vacate or make ineffectual or invalid something that previously was effectual or valid.
- vacate proceedings after the discovery of fraud
- vacate a grant of crown property
Quash is a strictly legal term applied chiefly to indictments thrown out of court as defective.