n. & v.
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.
[ ME f. OF fissure or L fissura f. findere fiss- cleave ]