infiltrate

(verb) cause (a liquid) to enter by penetrating the interstices.

(verb) enter a group or organization in order to spy on the members. Synonyms: penetrate. Example: "The student organization was infiltrated by a traitor."

(verb) pass into or through by filtering or permeating. Example: "The substance infiltrated the material."

(verb) pass through an enemy line; in a military conflict. Synonyms: pass through.