cleft

1. An opening, fissure, or V-shaped indentation made by or as if by splitting.
2. A piece made by splitting.

   a cleft of wood

3. A disease of horses; a crack on the band of the pastern.

verb

To syntactically separate a prominent constituent from the rest of the clause that concerns it, such as threat in "The threat which I saw but which he didn't see, was his downfall."

1. To split or sever something with, or as if with, a sharp instrument.

   The wings cleaved the foggy air.

2. To break a single crystal (such as a gemstone or semiconductor wafer) along one of its more symmetrical crystallographic planes (often by impact), forming facets on the resulting pieces.
3. To make or accomplish by or as if by cutting.

   The truck cleaved a path through the ice.

4. To split (a complex molecule) into simpler molecules.
5. To split.
6. Of a crystal, to split along a natural plane of division.

adjective

Split, divided, or partially divided into two.