1 syllable:
arm, bpharm, charm, charme, farm, flarm, harm, hdparm, larme, naarm, parme, pharm, scarm, sdarm, sharm, smarm, tharm

2 syllables:
a-arm, alarm, alarme, allarme, becharm, blinddarm, decharm, desarme, disarm, ducharme, ex-arm, firearm, fish-farm, forearm, gendarme, genpharm, gisarm, gisarme, guisarme, home-farm, iclarm, inarm, longarm, mallarme, non-farm, nonfarm, nufarm, polearm, prearm, proof-arm, pycharm, re-arm, rearm, round-arm, sadarm, schoolmarm, self-harm, short-arm, side arm, simfarm, small-arm, stiff-arm, straight-arm, strong-arm, strongarm, stud farm, tonearm, tone arm, tree farm, truck farm, tulkarm, unarm, uncharm, windfarm, yard-arm

3 syllables:
aquafarm, bioarm, buy the farm, canadarm, cattle farm, clarkson's farm, contact arm, countercharm, dairy farm, disencharm, funny farm, good luck charm, love alarm, moneyfarm, novopharm, over-arm, overarm, pickup arm, prison farm, rocker arm, sewage farm, smoke alarm, super-pharm, under-arm, underarm, unicharm, wiper arm, writing arm

4 syllables:
burglar alarm, collective farm, enobosarm, fire alarm, pneumatogarm, zonealarm

6 syllables:
allisyn ashley arm, repeating firearm

7 syllables:
automatic firearm

9 syllables:
semiautomatic firearm