2 letters:
os

3 letters:
bos, cos, dos, kos, las, mos, oss, pos, ros, vos

4 letters:
aase, blas, boss, bras, clos, coss, cros, daas, dazs, doss, foss, goss, haas, hahs, hoss, joss, kaas, kjos, klos, koss, loss, mohs, moss, noss, poss, ross, soss, toss, vohs, voss, vyas, wass, yoss, zoss

5 letters:
aaass, abbas, acoss, ammas, amoss, bloss, boiss, boss', bosse, bross, cauce, closs, cosse, cross, dross, fause, fauss, floss, fosse, fross, gloss, gosse, haase, haass, hamas, hasse, hnoss, iapss, jboss, josse, klaas, kloss, knous, kosse, kross, maass, mauss, mosse, motss, nauss, phos-, ploss, pross, quass, ross', rosse, sloss, stoss, swass, tomas, tosse, tross, vause, wasce

6 letters:
across, alsace, amboss, atroce, betoss, bombas, caguas, cedras, clauss, coloss, cross-, crosse, deboss, demoss, devoss, disoss, ecosse, emboss, endoss, fausse, feroce, flosse, glauce, gloss-, glosse, gotaas, grosse, hamas', hammas, helios, imboss, kiryas, knauss, koloss, kosmas, krause, lacoss, nahuas, omahas, pataas, retoss, rnaase, spross, stauss, vanoss, veloce, vsauce

7 letters:
bonasse, bugloss, cedras', chavous, chiasse, colosse, culross, danfoss, hammas', hooplas, incross, karakos, krausse, kutauss, lacross, lafosse, lazyass, macross, molosse, oakmoss, otpotss, patasse, phelios, recross, rubasse, schloss, shavous, stelios, uncross, virtuos

8 letters:
aruldoss, barabbas, candyass, clubmoss, cup-moss, dobcross, girlboss, isogloss, kephalos, lacrosse, lipgloss, loanloss, neuromas, omphalos, outcross, pangloss, paraguas, piraguas, ringtoss, soysauce, spectros, srinivas, terrasse, twycross, vandross, warcross, waycross

9 letters:
albatross, arkansass, autocross, backcross, beschloss, chandross, club-moss, demitasse, ditchmoss, holycross, hot-cross, la-crosse, ladislaus, lip-gloss, motocross, semigloss, shawcross, spikemoss, starcross, stonetoss, stop-loss, testcross, underboss

10 letters:
abul-abbas, applecross, applesauce, back-cross, beschloss', bucephalos, candyfloss, chihuahuas, crisscross, cyclocross, encephalos, exomphalos, fairyfloss, intercross, polocrosse, rallycross, recognosce, semi-gloss, shallcross, stanislaus, supercross, test-cross, wenceslaus

11 letters:
auchincloss, christcross, contrebasse, criss-cross, cyclo-cross, doublecross, erdgeschoss, precognosce, sinterklaas

12 letters:
cirsomphalos, double-cross, leineschloss, single-cross, sint-niklaas

13 letters:
floating-moss

14 letters:
carrickmacross, pitch-and-toss

8 letters:
thoughts