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, sauce, sloss, stoss, swass, tomas, tosse, tross, 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, pdd nos, phelios, recross, rubasse, schloss, shavous, stelios, uncross, virtuos

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

9 letters:
adin ross, albatross, arkansass, at a loss, autocross, backcross, ben cross, beschloss, bigg boss, chandross, club-moss, club moss, demitasse, ditchmoss, genus bos, go across, holycross, hot-cross, hot sauce, hugo boss, kyla ross, la-crosse, ladislaus, la crosse, lip-gloss, long moss, motocross, peat moss, red cross, rick ross, rose moss, semigloss, shawcross, soy sauce, spikemoss, starcross, stonetoss, stop-loss, testcross, underboss

10 letters:
abul-abbas, applecross, applesauce, april ross, back-cross, beard moss, beschloss', betsy ross, black moss, bucephalos, candyfloss, chihuahuas, crisscross, cut across, cyclocross, duck sauce, encephalos, exomphalos, fairyfloss, get across, hard sauce, intercross, irish moss, mint sauce, navy cross, party boss, plum sauce, polocrosse, put across, rallycross, recognosce, run across, scale moss, semi-gloss, shallcross, spike moss, stanislaus, straw boss, supercross, taco sauce, test-cross, trail boss, wenceslaus, wine sauce

11 letters:
apple sauce, arctic moss, auchincloss, bread sauce, brown sauce, caper sauce, chili sauce, christcross, come across, contrebasse, cream sauce, criss-cross, curry sauce, cyclo-cross, doublecross, erdgeschoss, fudge sauce, greek cross, latin cross, look across, marion ross, memory loss, papal cross, pass across, pasta sauce, peach sauce, precognosce, sinterklaas, steak sauce, white sauce

12 letters:
atticus ross, capital loss, celtic cross, charity toss, cheese sauce, cirsomphalos, dental floss, desmond doss, double-cross, double cross, garlic sauce, hearing loss, helluva boss, iceland moss, leineschloss, market cross, pepper sauce, sarah knauss, shrimp sauce, single-cross, sint-niklaas, spanish moss, tartar sauce, tomato sauce

13 letters:
anchovy sauce, apricot sauce, calvary cross, floating-moss, maltese cross, mustard sauce, newburg sauce, paprika sauce, randolph ross, reindeer moss, seafood sauce, tabasco sauce

14 letters:
barbecue sauce, burgundy sauce, carrickmacross, cocktail sauce, elisabeth moss, financial loss, hunter's sauce, katharine ross, lorraine cross, mushroom sauce, northern cross, pitch-and-toss, political boss, put one across, southern cross, victoria cross

15 letters:
chocolate sauce, cranberry sauce, hungarian sauce, jerusalem cross, lyonnaise sauce, profit and loss, spaghetti sauce

16 letters:
carrie-anne moss, little club moss, tyler winklevoss

17 letters:
bourguignon sauce, brown onion sauce, horseradish sauce, patriarchal cross, sign of the cross, tracee ellis ross, white onion sauce

18 letters:
betsy griscom ross, cameron winklevoss, insane clown posse, mushroom win sauce

19 letters:
chinese brown sauce, wandering albatross

21 letters:
bolognese pasta sauce, low st andrew's cross, murder of polly klaas, stations of the cross

23 letters:
conductive hearing loss

26 letters:
distinguished flying cross

27 letters:
distinguished service cross

8 letters:
thoughts

22 letters:
in everyone's thoughts