penetration has 2 distinct synonyms spread across 2 of its 6 senses. Each sense below keeps its own list, because a synonym belongs to a meaning and not to a word: swapping one sense's substitute into another sense's sentence is how a thesaurus makes writing worse. WordNet records no antonym for it — antonymy is a relation between word forms rather than concepts, so it is deliberately sparse.
Counts are distinct word forms across every sense. A synonym that appears under three senses is counted once here and shown three times below, under each sense it belongs to.
the act of entering into or through something
“the penetration of upper management by women”
the ability to make way into or through something
“the greater penetration of the new projectiles will result in greater injuries”
the depth to which something penetrates (especially the depth reached by a projectile that hits a target)
the act (by a man) of inserting his penis into the vagina of a woman
Synonyms, antonyms and the broader and narrower relations for penetration come from Princeton University’s WordNet. Full sources and licences.