From Longman Dictionary of Contemporary Englishrock-hardˌrock-ˈhard adjective 1 extremely hard The bread was stale and rock-hard.2 British EnglishSTRONG PERSON strong and not afraid of anyone – used humorously
Examples from the Corpus
rock-hard• Her father, under a soft, plump, vague appearance, was rock-hard.• It was rock-hard and dry as a biscuit.• Granny Weatherwax lay in it, her dress torn, her hair uncoiling from its rock-hard bun.• The result, taut abs, a rock-hard butt and twanging musculature, was still not enough to save her marriage.• As he stuck a sceptical thumb into a tub of rock-hard Camembert, he knew he was facing a first-class mess.• Tekla, the dark-eyed young Gentile woman with red cheeks, brought us tea and rock-hard kichel.• Many had protective foils like thorns and spines, with much of the plant tissue containing rock-hard phytoliths or tough fibrous cellulose. 