crevasse(n = noun.object) - a deep fissure;
is a kind of cleft, crack, crevice, fissure, scissure

1.  A deep crevice or fissure, as in embankment; one of the clefts or fissure by which the mass of a glacier is divided. [1913 Webster]

2.  A breach in the levee or embankment of a river, caused by the pressure of the water, as on the lower Mississippi. [1913 Webster]

crevasse, n.
1 a deep open crack, esp. in a glacier.
2 US a breach in a river levee.

Etymology:
F f. OF crevace: see CREVICE

N  interval, interspace, separation, break, gap, opening, hole, chasm, hiatus, caesura, interruption, interregnum, interstice, lacuna, cleft, mesh, crevice, chink, rime, creek, cranny, crack, chap, slit, fissure, scissure, rift, flaw, breach, rent, gash, cut, leak, dike, ha-ha, gorge, defile, ravine, canon, crevasse, abyss, abysm, gulf, inlet, frith, strait, gully, pass, furrow, abra, barranca, barranco, clove, gulch, notch, yawning gulf, hiatus maxime, hiatus valde deflendus, parenthesis, void, incompleteness, period, interim (time), with an interval, far between, breachy, rimose, rimulose, at intervals, longo intervallo.