1 syllable:
'em, 'm, -some, bd-rom, bluhm, brum, brumm, bum, chum, clum, cm sm, comme, crum, crumb, crumm, csc ssm, cum, ddrum, druim, drum, drumm, dslam, dum, dumb, dumm, dzbb-am, dzrj-am, from, frum, fsk im, gd-rom, glum, gmbh, gmm sm, grum, gthumb, gum, gumm, hb gam, hm, hmm, hp tim, hrtem, hum, humm, jlc csm, jpcg dimm, jstars gsm, khnum, klumb, krum, krumm, krumme, kumm, lum, lumb, lumm, lumme, lv sem, maam, mp gam, msd sm, msn im, mum, mumm, mumme, nccam, nd tem, ngcam, ns qam, numb, pflum, phlem, phleme, plum, plumb, pps sm, rhomb, rs tim, rum, schem, schrum, schtum, schum, schumm, scrum, scum, scumm, shrum, shtum, shum, skrim, slum, smd imb, smram, some, spf dbim, sp tcim, std ssm, strum, stum, stumm, stumme, sum, summe, swum, them, thrum, thum, thumb, thumm, tp fem, tshombe, um, umm, v-comb, vl-srsam, xrsam, yum

2 syllables:
aksum, alum, ancrum, bass drum, baucum, bay rum, beach plum, become, benumb, bethumb, bithumb, black gum, blue gum, boyum, brake drum, branscome, breadcrumb, cancrum, carum, checksum, columb, date from, date plum, deblum, dishyum, djarum, encom, exum, faiyum, first-come, flow from, freedumb, ghost gum, goodrum, goose plum, green thumb, guthrum, herefrom, hog plum, hohum, hop-thumb, humdrum, ikwum, income, keep from, keep mum, kim bum, larum, lump-sum, marum, mccrum, mccrumb, narum, neu-ulm, noucome, outcome, pileum, plethrum, pond scum, red drum, red gum, rose gum, sharum, shrink from, side drum, snare drum, snow gum, steak-umm, steel drum, stepmom, striped drum, succumb, swamp gum, sweet gum, tear-thumb, tecum, therefrom, tom thumb, unplumb, wellcome, wherefrom, wild plum, wring from, yab-yum, yum-yum, yumyum

3 syllables:
abstain from, adnexum, amarum, amphicome, august plum, barathrum, beetlebum, bongo drum, bubble gum, bungarum, cherry plum, chewing gum, cider gum, cocoa plum, coco plum, common plum, congo gum, damson plum, deaf-and-dumb, desist from, direct sum, disbecome, escape from, flooded gum, labarum, manna gum, mesquite gum, metal drum, misbecome, mishawum, moxie plum, natal plum, net income, no-see-um, norodom, obesum, overcome, physarum, podarthrum, pyrethrum, refrain from, river gum, rule-of-thumb, rule of thumb, saccharum, sisarum, sour gum, spirit gum, spotted gum, tartarum, tax income, tenor drum, tidy sum, unbecome, unbenumb, vector sum, water gum, zero-sum

4 syllables:
abomasum, arisarum, canada plum, carissa plum, chickasaw plum, dante exum, erucifrom, falciparum, forest red gum, glyoxysome, governor's plum, governor plum, granulosum, hedysarum, hop-o'-my-thumb, jamaica rum, japanese plum, marmalade plum, mountain swamp gum, pacific plum, peppermint gum, pigmentosum, principal sum, river red gum, senegal gum, shy away from, sierra plum, sonora gum, stay away from, stenotaphrum, unearned income

5 syllables:
alleghany plum, allegheny plum, eucalyptus gum, government income, madagascar plum, national income, personal income, tetrapharmacum

6 syllables:
american red plum, american sweet gum, disposable income, oleosaccharum, per capita income

8 syllables:
universal basic income