1. (superl.) Having the quality of flexibility without brittleness; yielding to force without breaking; capable of resisting great strain; as, the ligaments of animals are remarkably tough.

2. (superl.) Not easily broken; able to endure hardship; firm; strong; as, tough sinews.

3. (superl.) Not easily separated; viscous; clammy; tenacious; as, tough phlegm.

4. (superl.) Stiff; rigid; not flexible; stubborn; as, a tough bow.

5. (superl.) Severe; violent; as, a tough storm.

Antaeus Atlas Briareus Brobdingnagian Charles Atlas Cyclops Goliath Herculean Hercules Mafioso OK Polyphemus Samson Spartan Spartanic Superman Tarzan Titan Young Turk abiding abstruse ace-high acute adamant adamantine adherent adhesive age-long aged amylaceous ancient antique arbitrary arduous astringent athletic austere authoritarian backbreaking bad baffling bang-up battler beast beldam belligerent belted knight berserk berserker beyond one bickerer blade bomber bony bonzer boss bravo brawler brawny bruiser brutal brute bulky bulldogged bulldoggish bulldoggy bullheaded bully bullyboy burdensome burly but good callous cartilaginous cement cemental chewy chronic clabbered clammy clingy clotted coagulated cohesive cold colossus combatant competitor complex complicated concrete confirmed constant contender contestant continuing cool coriaceous corking corneous crabbed crackerjack cramp critical crushing curdled cutting dandy delicate delicious demanding demon dense devil diamondlike difficile difficult disputant diuturnal doughty doughy dour dragon drastic ducky duelist durable dure effortful enduring enforcer evergreen exacting excessive exigent exorbitant extravagant extreme fab fencer feuder fibrous fiend fierce fighter fighting cock fine and dandy fire-eater firebrand firm fixed flintlike flinty foilsman forced formidable furious fury game gamecock gamy garbled gaumy gear gelatinous giant gladiator glairy gluelike gluey glutenous glutinose glutinous gooey goon gorilla granitelike granitic great grim gristly gritty groovy grueling grumous gumbo gumbolike gumlike gummous gummy gun gunsel gutsy gutty hairy hard hard as nails hard to understand hard-bitten hard-boiled hard-earned hard-fought hard-line hard-nosed hard-set hardened hardhearted hardnose hardy harsh hatchet man heavy hefty hell-raiser hellcat hellhound hellion holy terror hood hoodlum hooligan horny hot hothead hotspur hunky-dory icy immoderate immutable incendiary inflexible inspissated intemperate intense intractable intransient intrepid intricate inured inveterate irksome iron-hard ironlike jam-up jawbreaking jelled jellied jellylike jouster jumbled just dandy keen killer killing