v. t. [ imp. & p. p. Invaded; p. pr. & vb. n. Invading. ] [ L. invadere, invasum; pref. in- in + vadere to go, akin to E. wade: cf. OF. invader, F. envahir. See Wade. ] [ 1913 Webster ]

1. To go into or upon; to pass within the confines of; to enter; -- used of forcible or rude ingress. [ Obs. ] [ 1913 Webster ]

Which becomes a body, and doth then invade
The state of life, out of the grisly shade. Spenser. [ 1913 Webster ]

2. To enter with hostile intentions; to enter with a view to conquest or plunder; to make an irruption into; to attack; as, the Romans invaded Great Britain. [ 1913 Webster ]

Such an enemy
Is risen to invade us. Milton. [ 1913 Webster ]

3. To attack; to infringe; to encroach on; to violate; as, the king invaded the rights of the people. [ 1913 Webster ]

4. To grow or spread over; to affect injuriously and progressively; as, gangrene invades healthy tissue.

Syn. -- To attack; assail; encroach upon. See Attack. [ 1913 Webster ]

v. i. To make an invasion. Brougham. [ 1913 Webster ]

n. One who invades; an assailant; an encroacher; an intruder. [ 1913 Webster ]

adj. same as invasive{ 1 }.
Syn. -- incursive, invasive. [ WordNet 1.5 +PJC ]

v. t. To insert as in a sheath; to produce intussusception in.

{ } a. (Biol.) (a) Sheathed. (b) Having one portion of a hollow organ drawn back within another portion. [ 1913 Webster ]

n. [ L. pref. in- + vagina sheath. ] [ 1913 Webster ]

1. (Biol.) The condition of an invaginated organ or part. [ 1913 Webster ]

2. The inward movement of the wall of a tissue or cell, to form a cavity; also, the cavity thus formed. [ PJC ]

3. Specifically: (Biol., Embryology) The inward movement of one part of the wall of a blastula, to form a gastrula; the process of gastrulation, in which layers of the ovum are differentiated. [ 1913 Webster +PJC ]

☞ In embolic invagination, one half of the blastosphere is pushed in towards the other half, producing an embryonic form known as a gastrula. -- In epibolic invagination, a phenomenon in the development of some invertebrate ova, the epiblast appears to grow over or around the hypoblast. [ 1913 Webster ]

n. [ L. invalescens, p. pr. of invalescere to become strong. See 1st In-, and Convalesce. ] Strength; health. [ Obs. ] [ 1913 Webster ]

a. Wanting health; valetudinary. [ R. ] [ 1913 Webster ]

v. t. 1. To make or render invalid or infirm. “Invalided, bent, and almost blind.” Dickens. [ 1913 Webster ]

2. To classify or enroll as an invalid. [ 1913 Webster ]

Peace coming, he was invalided on half pay. Carlyle. [ 1913 Webster ]