Definition of oak fly in English:

oak fly

noun

  • 1Either of two long-legged orange and brown dipteran flies of the genus Rhagio (formerly Leptis; family Rhagionidae), R. lineola and especially the larger R. scolopacea.

  • 2Angling an artificial fly imitating either of these.

Origin

Mid 17th century; earliest use found in Thomas Barker (fl. 1651), writer on angling.