Synonyms for Slit:

adj.

blemished (adjective)
flawed, disfigured, scraped, imperfect, Scored, splotched, marked, tainted, marred, impure, specked, gashed, scarred, discolored, deformed, blotched, pockmarked, Nicked, defective, damaged, blistered, freckled, tarnished, Scabbed, Hacked, distorted, notched, fractured, spotted, stained, cracked, blemished, scratched, defaced, flecked, spoiled, Scuffed, chipped, abraded.
gaping (adjective)
notched, broken, cracked, cleaved, breached, gaping.
notched (adjective)
Jogged, cracked, split, cut, chinked, indented, incised, gashed, notched, Scored, Nicked, serrated.

n.

crater, blowhole, cranny, channel, aperture, cavity. burn, bruise, help, blight, burnout, enter, slash, pierce, breakage. clip, chop, etch, assemble, cut out, dissever, cut-up, finely, carve. blemish (noun)
blotch, deformity, abrasion, defacement, rift, stigma, spoilage, weal, discoloration, scab, impurity, eyesore, imperfection, lesion, distortion, disfigurement, brand, sore, fault, drawback, wart.
gap (noun)
interval, space, gulf, cleft, break, crevice, ravine, gap, abyss, chasm, breach.
notch (noun)
serration, incision, jog, indentation, chink, indent.
opening (noun)
chink, split.
slit (noun)
injured, incision, scratch, cut, twat, puss, slitted, slice, dent.
small opening, cut (noun)
crevice, incision, split, gash, cleft, tear, aperture, fissure, breach, cleavage.
split (noun)
cleavage.

v.

blemish (verb)
dot, disfigure, notch, gash, taint, score, hurt, speck, kink, hack, scar, freckle, nick, discolor, deform, blot, mark, spot, defect, damage, blister, fracture, splotch, stain, spoil, distort, mar, fleck, scratch, scuff, chip, blemish, pockmark, deface, flaw, scrape, tarnish, check, abrade.
cut open (verb)
slice, pierce, slash, sever, incise, rip.
halve (verb)
divide, branch, split, cut, part, fork, halve, bisect, axe, bifurcate, rend, tear, sever, fissure, rupture, cleave, rip.
notch (verb)
incise, serrate.

Other synonyms:

dissever. pierce, slash. carve, channel. Other relevant words:
chop, cavity, breakage, channel, puss, dent, carve, twat, cleavage, dissever, cranny, injured, burn, aperture, slitted, slice, pierce, slash.

Usage examples for slit

  1. He took up the thin, steel, paper- knife from the desk and slit open the envelope. – The Clue of the Twisted Candle by Edgar Wallace
  2. 38 and cut the three- cornered catch in one half and the slit in the other half, as shown in Fig. – Little Folks' Handy Book by Lina Beard Adelia B. Beard
  3. See that little slit on the cheek up there? – The-Circus-Boys-on-the-Flying-Rings-or-Making-the-Start-in-the-Sawdust-Life by Darlington, Edgar B. P.