Definition from Wiktionary, the free dictionary
alderfly (plural alderflies)
- A member of any one of the sixty-six species of the Sialidae family of megalopteran insects, each specimen of which has a body length not exceeding one inch and possesses long filamentous antennae and four large dark wings.
- (fishing) An artificial fly with brown mottled wings, body of peacock harl, and black legs.
- (megalopteran insect): orl fly (angling)