Based on the context, a crevice means a small opening in the wall. The word crevice, comes from the Latin word "crepare" meaning to rattle or crack, and from the Old French word "crever" meaning, to burst. Therefore, the actual meaning of the word "crevice" is a small opening especially in a wall. Other words that have a similar meaning with crevice are: crack, fissure, slit and fracture.