Toughening rhymes with:
deafening, orphaning, siphoning, softening, stiffening, abandoning, airconditioning, apportioning, auctioning, auditioning, awakening, battening, beckoning, blackening, bludgeoning, boening, brightening, broadening, burdening, burgeoning, captaining, captioning, cautioning, championing, cheapening, chickening, christening, clendening, commissioning, conditioning, corpening, cushioning, dampening, darkening, deadening, deafening, decommissioning, deepening, dekoning, determining, disciplining, disheartening, disillusioning, enlightening, enlivening, envisioning, fashioning, fastening, fattening, flattening, freshening, frightening, functioning, gardening, glendening, glistening, groening, happening, hardening, harmening, hastening, heartening, heightening, imagining, imprisoning, jettisoning, kroening, leavening, lengthening, lessening, lightening, likening, listening, loosening, maddening, malfunctioning, margining, mentioning, moening, motioning, opening, optioning, orphaning, pardoning, partitioning, petitioning, poisoning, positioning, provisioning, questioning, quickening, rationing, reasoning, reawakening, reckoning, reconditioning, reexamining, reopening, repositioning, ripening, saddening, sanctioning, schoening, seasoning, sectioning, sharpening, shortening, sickening, siphoning, slackening, smartening, softening, stationing, stiffening, straightening, strengthening, summoning, sweetening, terpening, thickening, threatening, tightening, transitioning, tregoning, unquestioning, vacationing, weakening, widening, wilkening, worsening
Toughening sounds like:
tacking, tacoma's, taganka, tagging, takanashi, taking, takings, tasking, taxiing, taxing, teaching, teachings, teasing, technic, technics, technique, techniques, technomic, tecumseh, texan's, texans, thesing, thickening, thickens, thickness, thyssen's, ticinus, ticking, tokens, tokunaga, toscanini's, tossing, touching, toughens, toughness, toxins, tsang, tseng, tsiang, tsongas, tsongas', tsongas's, tucking, tudjman's, tugging, tusing, tussing, tweaking, twitching, tycoon's, tycoons, tyson's, tysons