linguistics:
in, is, it, us, cut, gin, gnu, gun, gut, its, lit, lug, nul, nit, nut, sin, sis, sit, sun, tic, tin, tug
<Gasp>
cist, clit, cult, cunt, cuss, cuts, gins, gist, glut, guns, guns, gust, guts, lint, list, lits, lugs, lung, lust, nils, nuts, scut, sign, silt, sing, sins, sits, slit, slug, slut, snug, stun, suit, sung, suns, tics, ting, tins, tugs, tung, unit, cling, clits, clung, cuing, cults, cunts, gists, glint, guilt, gusts, icing, lints, lists, lungs, signs, silts, sings, sinus, sling, slits, slugs, slung, sluts, snugs, sting, stung, stuns, suing, suits, tings, tunic, units, using,
citing, clings, glints, guilts, icings, insist, insult, siting, slings, stings, sunlit, tunics, cussing, insults, listing, lusting, lutings, slicing, suiting, linguist, listings, suitings, linguists, utilitsing.

<boulter.com/scrabble bonus>

"catastrophe"