—n.
1 an opening, usu. long and narrow, made esp. by cracking, splitting, or separation of parts.
2 Bot. & Anat. a narrow opening in an organ etc., esp. a depression between convolutions of the brain.
3 a cleavage.
—v.tr. & intr. split or crack.
Etymology: ME f. OF fissure or L fissura f. findere fiss- cleave
Useful english dictionary. 2012.