1. (Science: ornithology) A European bird (Corvus frugilegus) resembling the crow, but smaller. It is black, with purple and violet reflections. The base of the beak and the region around it are covered with a rough, scabrous skin, which in old birds is whitish. It is gregarious in its habits. The name is also applied to related Asiatic species. The rook . . . Should be treated as the farmer’s friend. (Pennant)
2. A trickish, rapacious fellow; a cheat; a sharper.
Origin: AS. Hrc; akin to OHG. Hruoh, ruoh, ruoho, Icel. Hrkr, Sw. Roka, Dan. Raage; cf. Goth. Hrukjan to crow.