Thesaurus

abominable, ambitious, arduous, atrocious, awful, awkward, bad, baffling, beardown, beefed-up, brawny, bullnecked, bullocky, calculating, calculative, callous, calloused, cartilaginous, case-hardened, catchy, challenging, chewy, comfortless, conniving, convulsive, coriaceous, corked, corky, crappy, dead, delicate, demanding, deplorable, desensitised, desensitized, difficult, disobedient, distressing, dreadful, dull, effortful, embarrassing, enured, evil, experienced, experient, fearful, ferocious, fibrous, fierce, fortified, fractious, frightful, full-fledged, fully fledged, furious, gristly, hard, hard-bitten, hard-boiled, hard-fought, hardened, hardy, hefty, hempen, herculean, hopeless, horrid, hostile, hot, icky, ill, incompetent, indigestible, indurate, industrial-strength, inedible, insensible, insensitive, intimate, inured, ironlike, irritating, knock-down, knock-down-and-drag-out, knockabout, knockdown-dragout, knockout, knotty, knowledgeable, lamentable, lashing, leathered, leatherlike, leathery, lousy, lurid, mediocre, merciless, mischievous, miserable, muscular, nasty, naughty, negative, no-good, noticeable, numb, old, older, pachydermatous, painful, pitiful, poisonous, poor, powerful, practiced, practised, pretty, problematic, problematical, pugnacious, raging, rampageous, reinforced, robust, rocky, rotten, rough, rubber, rubbery, ruffianly, rugged, sad, savage, scheming, seasoned, serious, severe, shrewd, sinewy, skilled, slam-bang, sorry, soulless, steely, sticky, stiff, stinking, stinky, strengthened, stringy, strong, sturdy, swingeing, tall, terrible, terrorist, thick-skinned, thickened, thorny, ticklish, tight, touchy, tough, tough-minded, tough-skinned, toughened, tricky, troublesome, trying, unaffected, unchewable, uncomfortable, uncool, uneasy, uneatable, unenviable, unfavorable, unfavourable, unmerciful, unpalatable, unpeaceful, unresponsive, unsentimental, unskilled, unspeakable, unsuitable, vehement, versed, veteran, vexed, violent, virile, warm, weapons-grade, weather-beaten, well-knit, well-set, worse, worst, wretched

tough is a ADJ.

bully, goon, hood, hoodlum, hooligan, punk, roughneck, rowdy, ruffian, street fighter, strong-arme, strong-armer, thug, tough, toughie, yob, yobb, yobbo, yobo

tough is a NOUN.