The Collaborative International Dictionary of English v.0.48:

Invade \In*vade"\, 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.]
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   1. To go into or upon; to pass within the confines of; to
      enter; -- used of forcible or rude ingress. [Obs.]
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            Which becomes a body, and doth then invade
            The state of life, out of the grisly shade.
                                                  --Spenser.
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   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.
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            Such an enemy
            Is risen to invade us.                --Milton.
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   3. To attack; to infringe; to encroach on; to violate; as,
      the king invaded the rights of the people.
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   4. To grow or spread over; to affect injuriously and
      progressively; as, gangrene invades healthy tissue.

   Syn: To attack; assail; encroach upon. See Attack.
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