intrusion, n. [encroachment], obtrusion, [infringement], interloping.
intrusive, a. [obtrusive]. Antonyms: unintrusive, [unobtrusive], [retiring].
intrust, v. [commit], confide.
invade, v. [infringe], [encroach], [trespass], intrench, [trench].
invalid, a. [null], [void], of no [efficacy]; [baseless], [unfounded].
invalid, a. valetudinary.
invalid, n. valetudinarian.
invalidate, v. [annul], [abrogate], [cancel], [quash], [nullify].
invalidation, n. [nullification], [abrogation], [annulment].
invalidism, n. valetudinarianism.