n. The act or process of penetrating between or within other substances; mutual penetration; also, the result of a process of interpenetration. Milman. [ 1913 Webster +PJC ]
n. [ L. penetratio: cf. F. pénétration. ]
And to each in ward part,
With gentle penetration, though unseen,
Shoots invisible virtue even to the deep. Milton. [ 1913 Webster ]
A penetration into the difficulties of algebra. Watts. [ 1913 Webster ]