1) Do secret-agent work 2) Filter 3) In a military conflict 4) Pass through an enemy line 5) Percolate 6) Permeate 7) Sink in 1) Enter 
• (v. t.) To penetrate gradually; -- sometimes used reflexively. • (v. i.) To enter by penetrating the pores or interstices of a substance; to filter into or through something.
To penetrate. If an IV infiltrates, the IV fluid penetrates the surrounding tissue. ... (12 Dec 1998) ... 
(in-fil´trāt) to penetrate the interstices of a tissue or substance. material so deposited; called also infiltration.
In·fil'trate intransitive verb [ imperfect & past participle Infiltrated ; present participle & verbal noun Infiltrating .] [ Prefix in- + filtrate : confer F, s'infiltrer . Confer Infilter .] To enter by pe...
Type: Term Pronunciation: in′fil-trāt, in-fil′trāt Definitions: 1. To perform or undergo infiltration. 2. A cellular infiltration (1) in the lung as inferred from appearance of a localized, ill-defined opacity on a chest radiograph; commonly used to describe a shadow on a radiograph. Synonyms: infiltration2
Infiltrate: To penetrate. If an IV infiltrates, the IV fluid penetrates the surrounding tissue.
an abnormal substance (eg. a cancer cell) in a tissue or organ
[v] - enter a group or organization in order to spy on the members 2. [v] - cause (a liquid) to enter by penetrating the interstices 3. [v] - pass into or through by filtering or permeating 4. [v] - pass through an enemy-line
penetrate verb enter a group or organization in order to spy on the members; `The student organization was infiltrated by a traitor`
to gain entry without being identified as not belonging