Meaning of “infiltrate” - Learner’s Dictionary

infiltrate

verb [ T ] us uk /ˈɪnfɪltreɪt/

to secretly join a group or organization so that you can learn more about them:

A journalist managed to infiltrate the gang of drug dealers.
infiltration noun [ C, U ] us uk /ˌɪnfɪlˈtreɪʃən/
infiltrator noun [ C ]

(Definition of “infiltrate” from the Cambridge Learner’s Dictionary © Cambridge University Press)