2 letters:
ox

3 letters:
cox, fox, lox, pox, rox, sox, vox

4 letters:
boxx, brox, coxe, docs, foxx, hbox, knox, laux, ochs, vaux, vocs, woks

5 letters:
adcox, anbox, araks, atrox, autox, bachs, balks, bebox, blocs, bochs, bocks, botox, calks, chocs, cocks, comox, crocs, cubox, d-tox, dachs, detox, docks, e-box, embox, faccs, falks, flocs, focks, gawks, glaux, groks, hawks, hocks, imbox, jocks, kkbox, lawks, lochs, locks, mawks, merox, minox, mocks, nocks, ochse, phlox, pocks, procs, redox, robox, rocks, s&box, s-box, sachs, sauks, socks, stoxx, t-box, taccs, talks, unbox, velox, vioxx, vivox, wachs, walks, x-box

6 letters:
airbox, amdocs, approx, avelox, baulks, binocs, bloc's, blocks, brocks, caulks, chalks, chocks, clocks, colfox, cowpox, crocks, dock's, dosbox, faulks, fawkes, flocks, flotox, folfox, frocks, hatbox, hawkes, heliox, hotbox, hydrox, icebox, in-box, iraq's, jawbox, jaycox, kidfox, knocks, kroc's, loches, lummox, mapbox, mattox, modocs, nitrox, outbox, outfox, pegbox, redbox, redfox, rhinox, rock's, runbox, salk's, sarbox, shocks, sigfox, simcox, skybox, smocks, stalks, stocks, talk's, tarbox, teabox, toybox, trimox, uproxx, yapoks

7 letters:
anammox, anaprox, arawaks, backbox, bandbox, beatbox, big-box, bloch's, block's, boombox, boondox, britbox, brock's, busybox, callbox, cashbox, castbox, chumbox, clock's, coolbox, cow-pox, deedbox, dicebox, digibox, dog-fox, dropbox, entonox, equinox, farebox, firebox, firefox, flummox, fluxbox, fowlpox, freebox, fundbox, gearbox, geexbox, gutwaks, hawke's, hellbox, infobox, jukebox, listbox, lockbox, longbox, luminox, mailbox, maniocs, milkpox, mohawks, musk-ox, okotoks, openbox, palafox, paradox, pillbox, playbox, polymox, pondoks, poorbox, postbox, rheboks, rockbox, rudebox, saltbox, sandbox, sea-fox, seedbox, shitbox, showbox, soapbox, spitbox, squawks, stock's, stocks', talkbox, textbox, thwacks, tickbox, toolbox, toy-box, undocks, unlocks, wallbox, willcox, woodcox, workbox

8 letters:
airlocks, audiovox, bedrocks, birchbox, blackbox, brainbox, breadbox, buildbox, camelpox, catwalks, checkbox, coachbox, colorocs, crashbox, defrocks, dice-box, dreambox, drop-box, econobox, elflocks, fetlocks, glovebox, goshawks, gunlocks, haycocks, hemlocks, homeobox, horsebox, horsepox, jacques', jaywalks, juke-box, librivox, lightbox, loosebox, lunchbox, macaques, matchbox, moneybox, mousepox, nunataks, oarlocks, orthodox, otterbox, padlocks, paintbox, paradoxe, peacocks, petcocks, philodox, phonebox, photobox, play-box, postdocs, restocks, rockshox, rowlocks, salt-box, saucebox, scripbox, seacocks, seahawks, shylocks, skyhawks, skywalks, sleepbox, slingbox, slushbox, smallpox, smokebox, snuffbox, sonicfox, soundbox, stompbox, sweatbox, swiftfox, swinepox, tool-box, trisenox, unblocks, unfrocks, voicebox, warlocks, waterfox, waterpox, wedlocks, whitebox, whitepox, wileyfox

9 letters:
badblocks, ballcocks, black-box, boondocks, brant-fox, bufferbox, buzzcocks, cakewalks, candlebox, chromebox, cigar-box, deadlocks, ditty-box, dry-docks, eyestalks, firelocks, flintobox, gamecocks, gogglebox, gridlocks, groovebox, gunstocks, hancock's, havelocks, headlocks, heterodox, hungrybox, klipdachs, letterbox, linstocks, litterbox, lovefoxxx, lovelocks, mandelbox, megalobox, monkeypox, moonwalks, moorcocks, penstocks, pepperbox, picklocks, pillarbox, piratebox, pseudodox, rabbitpox, rattlebox, rhythmbox, searchbox, shadowbox, shamrocks, sherlocks, sidewalks, small-pox, snuff-box, spiritbox, stopcocks, strongbox, sunblocks, swine-pox, tinderbox, tomahawks, touch-box, traprocks, underdaks, warlock's, woodcocks

10 letters:
anachronox, backblocks, bag-in-box, beanstalks, billycocks, blackhawks, boardwalks, calliphlox, cellblocks, chatterbox, chickenpox, ciclopirox, cornstalks, crosswalks, dreadlocks, echohawk's, feedstocks, flintlocks, flying-fox, folfirinox, foreshocks, goggle-box, goldilocks, goldylocks, gridlock's, headstocks, hollyhocks, incredibox, interlocks, leafstalks, letter-box, matchlocks, moneytalks, nifurtimox, nighthawks, overstocks, paddle-box, pepper-box, phonebloks, roadblocks, rootstocks, sceloglaux, shadow-box, shamrock's, sherlock's, sleepwalks, spacewalks, squeezebox, tenfourfox, terrahawks, thunderbox, tinder-box, unorthodox, victorinox, virtualbox, whipstocks

11 letters:
aftershocks, alpenstocks, alphablocks, amphibrachs, badderlocks, blackhawk's, chicken-pox, diamondprox, fischbach's, hammerlocks, hitchcock's, outsidexbox, pouncet-box, silverhawks, squeeze-box, witness-box

12 letters:
birkenstocks, breechblocks, neo-orthodox, numberblocks, shuttlecocks, sparrowhawks, spatterdocks, weathercocks

13 letters:
band-in-a-box, chocolate-box, lightinthebox, saint-jacques, ultraorthodox

14 letters:
laughingstocks, omgitsfirefoxx, pseudosmallpox, rickettsialpox

15 letters:
jack-in-the-box, jewish-orthodox

16 letters:
jacks-in-the-box

3 letters:
ops

4 letters:
pops, cops, hops, tops, sops

5 letters:
elops, crops, shops, stops, slops, flops, props, copse, chops, drops

6 letters:
eumops, triops

7 letters:
lithops

8 letters:
aegilops, rynchops

9 letters:
anomalops, synagrops

11 letters:
parascalops

13 letters:
leptotyphlops, microdipodops