1 syllable:
acts, ax, axe, backes, backs, bax, black's, blacks, blacks', blacs, bracks, cac's, caq's, clacks, claques, cracks, daccs, dacks, dacs, dax, dax', dracs, dtracs, facce, fax, flachs, flacks, flaks, flax, fracs, hacks, haq's, jack's, jacks, jacques', jaques, knacks, lac's, lachs, lacks, lakhs, lax, mac's, mack's, macks, macs, max, maxx, nste acs, ntacs, pac's, packs, pacs, pacts, pakse, pax, plack's, plaques, plax, quacks, racks, rax, saccs, sachs, sachs', sacks, sacques, sacs, saks, sax, saxe, shacks, slacks, slaxx, smacks, snacks, spacs, stac's, stacks, stacs, tachs, tacks, tax, track's, tracks, trax, traxx, vax, wacks, wax, whacks, wracks, yacks, yax, zack's, zacks, zzzax

2 syllables:
addax, aipac's, ajax, amtrak's, anzacs, attacks, audax, awacs, backpacks, backtracks, banjax, bataks, baumax, baymax, bees-wax, beeswax, blackjacks, blendax, bluestacks, bootblacks, bootjacks, borax, brasstracks, break-axe, breakax, breakaxe, britax, broad-axe, broadax, broadaxe, bushwhacks, buybacks, callbacks, carfax, carjacks, ceefax, chaffwax, cheapjacks, chillax, chirac's, climax, cognacs, colfax, comebacks, compaq's, contacts, contax, coolmax, corax, cutbacks, death tax, dewax, dimacs, drawbacks, earth wax, earwax, eastpac's, emacs, ex-lax, fairfax, fairtax, fallax, fallbacks, fastbacks, fastracks, fig wax, filmax, finbacks, flapjacks, flashbacks, flomax, floor wax, fullbacks, galax, gift tax, gimcracks, givebacks, goobacks, gopac's, gravlax, greenback's, greenbacks, half-tracks, halfbacks, hapax, hardbacks, hardtacks, harpax, hatchbacks, haystacks, hdtracks, hijacks, hogbacks, holdbacks, humpbacks, hunchbacks, ice ax, ice axe, imacs, imax, imax', impacts, instax, intacs, ipecacs, joymax, kgbvax, kickbacks, kipchaks, klymaxx, knapsacks, knick-knacks, knickknacks, kodak's, koufax, kremvax, krymchaks, lac wax, land tax, leasebacks, lilacs, limax, lomax, lorax, madlax, malax, mandrax, mastax, mathjax, mcvax, meataxe, mendax, midpac's, mossbacks, muntjacs, mytracks, newsmax, opax, packsacks, packwax, panchax, parmacs, paxwax, paybacks, pentax, picaxe, pickax, pickaxe, pimax, playbacks, poll-tax, pollax, pollaxe, poll tax, pre-tax, pretax, pullbacks, q-max, qmax, racetracks, ransacks, re/max, redbacks, relax, repacks, ridgebacks, rollbacks, rotax, rothwax, rucksacks, sales tax, sam & max, scale wax, schweinshaxe, seatbacks, setbacks, shellacs, shoeblacks, showmax, sidetracks, skewbacks, skipjack's, skipjacks, ski wax, skyjacks, slingbacks, smilax, smokestacks, snorlax, snowpacks, soulwax, soundtracks, spacemacs, spalax, spantax, stamp tax, storax, supplejacks, surtax, switchbacks, syntax, tailbacks, tampax, tarmacs, tay-sachs, tecdax, terrax, thermax, throwbacks, thumbtacks, tiebacks, toad-flax, toadflax, trossachs, ty-sachs, unlax, unpacks, vivax, wattstax, wefax, westpac's, wi-max, wimax, wisecracks, wood-wax, xemacs, zwiebacks

3 syllables:
ader wax, afc ajax, affymax, aframax, after-tax, aftertax, almanacks, almanacs, amberjacks, animax, anoraks, antitax, applejacks, armagnacs, atarax, audimax, ava max, bangavax, battle-ax, battle-axe, bithorax, blasterjaxx, bosniacs, brainiacs, cadillac's, cadillacs, canvasbacks, carapax, cardiacs, celiacs, cluniacs, common ax, common axe, corbevax, cornerbacks, crackerjacks, cul-de-sacs, dagger-axe, dayton ax, dayton axe, devil's flax, diamondbacks, direct tax, disclimax, ecotax, edimax, equifax, erymax, estate tax, excise tax, filofax, fireman's ax, fireman's axe, florafax, fosamax, franchise tax, garrulax, give the axe, glycine max, gonyaulax, gravadlax, gunnysacks, halifax, handymax, haversacks, hidden tax, iatacs, income tax, interfax, japan wax, leatherbacks, license tax, lumberjacks, macintax, mbalax, microvax, minimax, miramax, mullenax, natterjacks, neoax, novavax, numberjacks, officemax, omnifax, omnimax, openstax, osedax, overtax, overwax, paperbacks, parallax, petromax, piggybacks, pontiac's, pontiacs, pricklebacks, quarterbacks, razorback's, razorbacks, sassenachs, scolopax, scramasax, sealing-wax, sealing wax, seawaymax, shadowfax, silverbacks, single tax, stack-o-tracks, steeplejacks, sticklebacks, subclimax, suezmax, supermac's, supermax, supertax, sycorax, telefax, terramax, thoroughwax, totonacs, transfer tax, trichoplax, turbotax, uemacs, vasomax, weatherwax, western ax, western axe, wolenzac's, xtacacs, zithromax, zodiacs

4 syllables:
737-max, amnesiacs, anticlimax, byrdmaniax, carnauba wax, chylothorax, coeliacs, counter-attacks, counterattacks, demoniacs, elegiacs, endolimax, entothorax, fitgirl repacks, gasoline tax, genethliacs, genus galax, haemothorax, hbo max, hemithorax, hemoothorax, hemothorax, hylophylax, indirect tax, insomniacs, mesothorax, metasyntax, metathorax, microemacs, micrognuemacs, mineral wax, morphosyntax, myeloplax, navitoclax, nycticorax, paraffin wax, paranoiacs, parodontax, plectrophenax, pneumothorax, progressive tax, property tax, pyothorax, pyrrhocorax, radiofax, simoniacs, squalicorax, stenothorax, stepmaniax, vegetable wax, venetoclax, withholding tax

5 syllables:
802.11ax, animaniacs, boeing 737 max, capital gains tax, caterpillar tracks, cephalothorax, dipsomaniacs, egomaniacs, estimated tax, haematothorax, hemophiliacs, henrietta lacks, hermann maurice saxe, inheritance tax, kleptomaniacs, monomaniacs, nymphomaniacs, phalacrocorax, plagioclimax, pneumatothorax, pyopneumothorax, pyromaniacs, sexual climax, stellar parallax, value-added tax, vvo2max

6 syllables:
2011 norway attacks, annual parallax, d.c. sniper attacks, diurnal parallax, expectiminimax, haemopneumothorax, hemopneumothorax, hydropneumothorax, megalomaniacs, pneumohemothorax, pneumopyothorax, pyohemothorax

7 syllables:
2008 mumbai attacks, geocentric parallax, horizontal parallax, last tango in halifax

8 syllables:
september 11 attacks

10 syllables:
declaration of estimated tax

11 syllables:
november 2015 paris attacks