3 letters:
axe, bax, dax, fax, lax, max, pax, rax, sax, tax, vax, wax, yax

4 letters:
acts, ajax, dacs, dax', flax, imax, macs, maxx, opax, pacs, plax, qmax, sacs, saks, saxe, trax

5 letters:
addax, audax, awacs, backs, blacs, borax, cac's, caq's, corax, daccs, dacks, dewax, dracs, emacs, facce, flaks, fracs, galax, hacks, hapax, haq's, imacs, imax', jacks, lac's, lachs, lacks, lakhs, limax, lomax, lorax, mac's, macks, malax, mcvax, neoax, ntacs, pac's, packs, pacts, pakse, pimax, q-max, racks, relax, rotax, saccs, sachs, sacks, slaxx, spacs, stacs, tachs, tacks, traxx, unlax, vivax, wacks, wefax, wimax, yacks, zacks, zzzax

6 letters:
animax, anzacs, atarax, backes, banjax, bataks, baumax, baymax, blacks, bracks, britax, carfax, ceefax, clacks, climax, colfax, contax, cracks, dimacs, dtracs, earwax, ecotax, edimax, erymax, ex-lax, fallax, filmax, flachs, flacks, flomax, harpax, iatacs, instax, intacs, jack's, jaques, joymax, kgbvax, knacks, koufax, lilacs, mack's, madlax, mastax, mbalax, mendax, osedax, paxwax, pentax, picaxe, pickax, pollax, pretax, quacks, re/max, sachs', shacks, slacks, smacks, smilax, snacks, spalax, stac's, stacks, storax, surtax, syntax, tampax, tecdax, terrax, tracks, uemacs, whacks, wi-max, wracks, xemacs, zack's

7 letters:
737-max, affymax, aframax, aipac's, anoraks, antitax, attacks, audimax, beeswax, black's, blacks', blendax, breakax, broadax, carapax, celiacs, chillax, claques, cognacs, coolmax, equifax, fairfax, fairtax, filofax, fosamax, gopac's, gravlax, halifax, hijacks, impacts, ipecacs, klymaxx, kodak's, kremvax, mandrax, maniacs, mathjax, meataxe, minimax, miramax, newsmax, novavax, omnifax, omnimax, overtax, overwax, packwax, panchax, parmacs, pickaxe, plack's, plaques, pollaxe, pre-tax, repacks, rothwax, sacques, showmax, snorlax, soulwax, spantax, suezmax, sycorax, tarmacs, telefax, thermax, track's, unpacks, vasomax, vvo2max, xtacacs, zodiacs

8 letters:
802.11ax, aftertax, almanacs, amtrak's, bangavax, bees-wax, bithorax, bosniacs, breakaxe, broadaxe, buybacks, cardiacs, carjacks, chaffwax, chirac's, cluniacs, coeliacs, compaq's, contacts, corbevax, cutbacks, elegiacs, finbacks, florafax, garrulax, goobacks, handymax, hdtracks, hogbacks, interfax, jacques', kipchaks, macintax, microvax, midpac's, mullenax, muntjacs, mytracks, openstax, parallax, paybacks, petromax, poll-tax, pontiacs, radiofax, ransacks, redbacks, scolopax, setbacks, shellacs, skyjacks, supermax, supertax, terramax, tiebacks, toadflax, totonacs, turbotax, ty-sachs, wattstax, wood-wax

9 letters:
after-tax, almanacks, amnesiacs, armagnacs, backpacks, battle-ax, bootjacks, brainiacs, break-axe, broad-axe, cadillacs, callbacks, comebacks, demoniacs, disclimax, drawbacks, eastpac's, endolimax, fallbacks, fastbacks, fastracks, flapjacks, fullbacks, gimcracks, givebacks, gonyaulax, gravadlax, halfbacks, hardbacks, hardtacks, haystacks, holdbacks, humpbacks, kickbacks, knapsacks, krymchaks, mossbacks, myeloplax, officemax, packsacks, playbacks, pontiac's, pullbacks, pyothorax, rollbacks, rucksacks, scramasax, seatbacks, seawaymax, shadowfax, simoniacs, skewbacks, skipjacks, snowpacks, spacemacs, subclimax, tailbacks, tay-sachs, toad-flax, trossachs, westpac's, zithromax, zwiebacks

10 letters:
amberjacks, animaniacs, anticlimax, applejacks, backtracks, battle-axe, blackjacks, bluestacks, bootblacks, bushwhacks, byrdmaniax, cadillac's, cheapjacks, dagger-axe, egomaniacs, entothorax, flashbacks, greenbacks, gunnysacks, hatchbacks, haversacks, hemithorax, hemothorax, hunchbacks, hylophylax, insomniacs, leasebacks, mesothorax, metasyntax, metathorax, microemacs, navitoclax, nycticorax, paperbacks, paranoiacs, parodontax, piggybacks, racetracks, razorbacks, ridgebacks, sassenachs, shoeblacks, sidetracks, skipjack's, slingbacks, stepmaniax, supermac's, throwbacks, thumbtacks, trichoplax, venetoclax, weatherwax, wisecracks, wolenzac's

11 letters:
blasterjaxx, brasstracks, canvasbacks, chylothorax, cornerbacks, cul-de-sacs, genethliacs, greenback's, haemothorax, half-tracks, hemoothorax, knickknacks, lumberjacks, monomaniacs, natterjacks, numberjacks, pyromaniacs, pyrrhocorax, razorback's, sealing-wax, silverbacks, smokestacks, soundtracks, squalicorax, stenothorax, supplejacks, switchbacks, thoroughwax

12 letters:
crackerjacks, diamondbacks, dipsomaniacs, hemophiliacs, knick-knacks, leatherbacks, morphosyntax, plagioclimax, pneumothorax, pricklebacks, quarterbacks, schweinshaxe, steeplejacks, sticklebacks

13 letters:
cephalothorax, haematothorax, kleptomaniacs, megalomaniacs, micrognuemacs, nymphomaniacs, phalacrocorax, plectrophenax, pyohemothorax

14 letters:
counterattacks, expectiminimax, pneumatothorax, stack-o-tracks

15 letters:
counter-attacks, pneumopyothorax, pyopneumothorax

16 letters:
hemopneumothorax, pneumohemothorax

17 letters:
haemopneumothorax, hydropneumothorax

4 letters:
taps, maps, gaps, caps

5 letters:
wraps, lapse, traps, facts, flaps, craps, capps

6 letters:
scraps, elapse, reacts, straps

7 letters:
perhaps, relapse, schnaps

8 letters:
collapse, schnapps, attracts, prolapse

9 letters:
contracts, pezophaps

10 letters:
aspidelaps

12 letters:
rhynchoelaps

14 letters:
dendrocolaptes