tough as nails

hard healthy resilient solid stiff tenacious tight vigorous

firm fit hardy stalwart stout

brawny cohesive conditioned dense durable fibrous flinty hard as nails hard-bitten hardened indigestible inflexible leathery lusty mighty molded resistant rigid robust rugged seasoned sinewy steeled strapping unbreakable unyielding withstanding

slack soft weak

delicate fragile unstable vulnerable wobbly