The Collaborative International Dictionary of English v.0.48:

Scissure \Scis"sure\, n. [L. scissura, from scindere, scissum,
   to cut, split.]
   A longitudinal opening in a body, made by cutting; a cleft; a
   fissure. --Hammond.
   [1913 Webster]

WordNet (r) 3.0 (2006):

scissure
    n 1: a long narrow opening [syn: crack, cleft, crevice,
         fissure, scissure]

Moby Thesaurus II by Grady Ward, 1.0:

70 Moby Thesaurus words for "scissure":
   abysm, abyss, arroyo, box canyon, breach, break, canyon, cavity,
   chap, chasm, check, chimney, chink, cleft, cleuch, clough, col,
   coulee, couloir, crack, cranny, crevasse, crevice, cut, cwm,
   defile, dell, dike, ditch, donga, draw, excavation, fault, fissure,
   flaw, flume, fracture, furrow, gap, gape, gash, gorge, groove,
   gulch, gulf, gully, hole, incision, joint, kloof, leak, moat,
   notch, nullah, opening, pass, passage, ravine, rent, rift, rime,
   rupture, seam, slit, slot, split, trench, valley, void, wadi