| Noun | 1. | Hieracium - large genus of perennial hairy herbs of Europe to western Asia to northwestern Africa and North America; few are ornamental; often considered congeneric with Pilosellaasterid dicot genus - genus of more or less advanced dicotyledonous herbs and some trees and shrubs hawkweed - any of numerous often hairy plants of the genus Hieracium having yellow or orange flowers that resemble the dandelion | |