2 letters:
op

3 letters:
bop, cop, fop, hop, lop, mop, opp, pop, sop, top

4 letters:
atop, bopp, chop, copp, crop, dopp, drop, flop, glop, hopp, jopp, kaup, knop, kopp, lopp, paap, paup, plop, popp, prop, raap, raup, ropp, shop, skop, slop, sopp, stop, swap, topp, yopp

5 letters:
aesop, alaap, bebop, bibop, bipap, c-pop, cesap, chopp, co-op, coppe, cropp, depop, doppe, estop, galop, gotop, gropp, ha hp, hoppe, hysop, iftop, ircop, j-pop, jawop, joppe, k-map, k-pop, kaupp, klopp, knaup, knopp, koppe, kropp, lihop, lmnop, loppe, losap, metop, mflop, mosop, necop, netop, no-op, paape, palop, picop, poppe, preop, propp, psyop, raupe, raupp, rebop, scaup, schop, serap, shopp, sicop, ska-p, slaap, staup, stopp, strop, swapp, synop, sysop, t-top, tropp, ukrop, v-pop, whaap, whaup, zztop

6 letters:
allsop, alltop, artpop, be-bop, bedhop, bedrop, bejape, bitpop, capwap, carhop, cartop, chanop, csicop, cyclop, daytop, doowop, dunlop, f-stop, galopp, haspop, hysope, instop, joypop, labtop, loplop, mandap, maypop, mmmbop, nettop, omgpop, opshop, outtop, paysop, postop, pre-op, redtop, schaap, schopp, shoppe, t-stop, tacsop, tiptop, unpope, unprop, unscop, unstop, upprop, webtop

7 letters:
afropop, allkpop, allsopp, alt-pop, antipop, archtop, art pop, bar hop, bed-hop, bed hop, bellhop, big top, bioyiop, bo-kaap, britpop, cedefop, coin-op, cooktop, copshop, cowflop, crowhop, desktop, dewdrop, doo-bop, doo-wop, droptop, dry mop, dustmop, eardrop, eggdrop, escalop, europop, eyedrop, flattop, foretop, gigapop, ginshop, go-stop, gumdrop, hardtop, hightop, hilltop, hip-hop, interop, job-hop, jonswap, joydrop, kashyap, killpop, konotop, maintop, man-ape, maximop, milksop, nonstop, op-shop, outcrop, overtop, palmtop, peg-top, peg top, petscop, photoop, pitprop, pop-top, popshop, post-op, preflop, red-top, rhodope, ripstop, robocop, robopop, rollmop, rolltop, rooftop, sawstop, schoppe, schropp, seedlop, sexshop, she-bop, shopbop, shuswap, sodapop, soursop, tanktop, teashop, timecop, tip-top, topshop, toyshop, treetop, tschopp, ttiwwop, uniswap, vipshop, wardrop, wolfcop, worktop

8 letters:
afgncaap, afro-pop, agitprop, air-drop, asterope, attercop, autostop, backdrop, backstop, bakeshop, bell-hop, blacktop, bloodpop, bookshop, bookstop, brainpop, bus-stop, bus stop, cantopop, city pop, clifftop, cookshop, cybercop, dew-drop, doorstop, dramshop, dust mop, eavedrop, ednaswap, evesdrop, eye-drop, firestop, flat-top, flip-top, flipflop, folk-pop, footdrop, gamestop, gigaflop, gimpshop, greentop, grogshop, halebopp, hat shop, hedgehop, helistop, high-top, hiveswap, hockshop, hot-swap, housetop, huniepop, hyperpop, lambchop, lollipop, lollypop, malaprop, mandopop, megaflop, milkdrop, ministop, moroshop, namedrop, non-stop, one-stop, open-top, openldap, orbitrap, overcrop, paradrop, patnitop, pawnshop, petaflop, pet shop, porkchop, post-bop, raindrop, rasterop, ridgetop, roll-top, rosedrop, roundtop, screwtop, shoeshop, skin-pop, skin pop, skunktop, slopshop, slutdrop, snowdrop, soda pop, soft-top, stovetop, supercop, sweetsop, synthpop, tabletop, tank top, teardrop, techshop, teleshop, teraflop, tokyopop, trip-hop, tuckshop, ultrapop, ultratop, wallapop, whip top, whitetop, wild hop, wineshop, wingstop, workshop

9 letters:
aftercrop, auto-stop, avant-pop, bellyflop, bubbletop, bunny-hop, carrottop, chisanbop, chop-chop, chop shop, clip-clop, clop-clop, dance-pop, eavesdrop, enveloppe, fetty wap, flag stop, flip-flop, flue stop, food shop, foot-drop, freezepop, full stop, futurepop, gift shop, hale-bopp, head shop, horseknop, intercrop, intershop, junk shop, lamb-chop, lindy hop, long-stop, name-drop, open shop, paintshop, parknshop, penshoppe, phoneshop, photoshop, polytrope, printshop, reed stop, root crop, round top, screw-top, sharecrop, shoe-shop, shoe shop, shortstop, skip-stop, speed cop, splashtop, stonecrop, sweatshop, sweet-sop, sweetshop, synth-pop, table-hop, talk shop, tangwhaup, technopop, tuck-shop, tuck shop, turboprop, underprop, woodentop, wristdrop, x.desktop, yellowtop

10 letters:
.full-stop, barbershop, belly-flop, belly flop, carrot-top, catch crop, coffeeshop, common hop, cornershop, cough drop, countertop, cover crop, dress shop, electropop, feathertop, field-crop, ginger pop, halter-top, island-hop, island hop, night-stop, organ stop, pizza shop, prestashop, print shop, rattle-top, record hop, ribbentrop, securedrop, short-stop, spindletop, sponge mop, take a hop, thriftshop, truck stop, turban-top, union shop, wrist-drop

11 letters:
beauty shop, bucket shop, cashmoneyap, channel-hop, closed-shop, closed shop, coffee shop, dichlorprop, double-crop, double-prop, double-stop, drag-n-drop, humming top, mom-and-pop, mountaintop, mutton chop, repair shop, riding crop, running pop, single prop, traffic cop, whistlestop, whiting-mop, window-shop

12 letters:
american hop, butcher shop, cowboy bebop, european hop, florist shop, glottal stop, hunting crop, japanese hop, machine shop, novelty shop, over-the-top, post-britpop, sophisti-pop, spinning top, suction stop, tobacco shop, whipping top, whistle-stop, whistle stop

13 letters:
drag-and-drop, knocking-shop, matthew hoppe, mirko cro cop

14 letters:
motorcycle cop, potential drop, transderm-scop

15 letters:
comparison-shop, worldstarhiphop

16 letters:
compare-and-swap

17 letters:
beverly hills cop, parupalli kashyap

18 letters:
sheltered workshop, the best of zz top

19 letters:
alternative hip hop

21 letters:
chrome remote desktop

29 letters:
words bubble up like soda pop