ETYM Old Eng. crevace, crevice. French crevasse, from crever to break, burst, from Latin crepare to crack,break. Related to Craven, Crepitate, Crevasse.
A long narrow depression in a surface; SYN. cranny, crack, fissure, chap.

ETYM Written also reft.
1. A gap between cloud masses.
2. A narrow fissure in rock.