hognut noun5 •(UK) A tuberous plant of family Apiaceae (Conopodium majus). •Black cumin of family Apiaceae. (Bunium bulbocastanum). •(US) A pignut or hickory tree (Carya glabra of family Juglandaceae). •Certain rushpeas, particularly Hoffmannseggia glauca (syn. Hoffmannseggia densiflora) Indian rushpea, of the Fabaceae. •A plant of species Mesosphaerum suaveolens (syn. Hyptis suaveolens), of family Lamiaceae. formshognuts