Definition of: infiltrate

(in·fil′trāt; esp. for v. defs. 2, 3 in′fil·trāt) v. ·trat·ed, ·trat·ing v.t.
1. To cause (a liquid or gas) to pass into or through pores or interstices.
2. To filter through or into; permeate.
3. Mil. To pass through, as enemy lines, singly or in small groups so as to attack from the rear or on the flanks.
—v.i.
4. To pass into or through a substance, as in filtering.
—noun
1. That which infiltrates or has infiltrated.
2. Any morbid substance that passes into the tissues of the body.