1go into or through (something), especially with force or effort:the shrapnel had penetrated his head [no object]:tunnels that penetrate deep into the earth’s core
(of a man) insert the penis into the vagina or anus of (a sexual partner).
2gain access to (an organization, place, or system), especially when this is difficult to do:M15 had been penetrated by Russian intelligence
(of a company) begin to sell its products in (a particular market or area):the company has succeeded in penetrating Western motorcycle markets
3succeed in understanding or gaining insight into (something complex or mysterious):I could never penetrate his thoughts
[no object] be fully understood or realized by someone:as his words penetrated, she saw a mental picture of him with Dawn
