A crevice is a long, tight space often found on the face of a mountain or other geological formation. A crevice can be large or small, but because it is usually hard reach, it is a great hiding place for all things like reptiles, bugs, and lost climbers.
The word crevice often refers to a natural formation, but it can be used to describe any long, narrow space that’s hard to access. If you’ve lost something you might say, “I’m going to look in every crack and crevice,” to describe the search. Chances are you’ll find that lost item in the long narrow space — the crevice — between the cushions of your sofa, along with other things you didn't even know were missing!