interpenetrat

v. i. To penetrate each the other; to penetrate between bodies or their parts. [ 1913 Webster ]

Interpenetrating molding (Arch.), in late Gothic architecture, a decoration by means of moldings which seem to pass through solid uprights, transoms, or other members; often, two sets of architectural members penetrating one another, in appearance, as if both had been plastic when they were put together. [ 1913 Webster ]

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 ]