He’s a man of integrity! What sort of man is he? He’s an integ ....... Hmmm, wait a minute.
It’s a little odd that there should be no adjective corresponding in sense to the noun. (Integral is no good, of course.) Not so much odd that there isn’t one but that the ones we had all withered on the vine. These were (I may have missed some) integritive, integrious, integrous and integre, all having the sense ‘marked by integrity, upright, honest’, etc and all noted as obs., rare in OED.
Ah well, no accounting for language, synonyms ably took up the slack. (Of the four though I quite like integrious, it has the right ring to it. Maybe I’ll run it up the flagpole down at the pub, see if anybody salutes.)
Any other nouns with no adjectives to support them?