fissure
1. Anatomy a narrow split or groove that divides an organ such as the brain, lung, or liver into lobes
2. a small unnatural crack in the skin or mucous membrane, as between the toes or at the anus
3. a minute crack in the surface of a tooth, caused by imperfect joining of enamel during development
Collins Discovery Encyclopedia, 1st edition © HarperCollins Publishers 2005
fissure
[′fish·ər] (geology)
A high, narrow cave passageway.
An extensive crack in a rock.
(metallurgy)
A small cracklike discontinuity with a slight opening or displacement of the fracture surfaces.
McGraw-Hill Dictionary of Scientific & Technical Terms, 6E, Copyright © 2003 by The McGraw-Hill Companies, Inc.