'boat fly' definitions:
Definition of 'boat fly'
From: GCIDE
- Boat bug \Boat" bug`\ (Zool.) An aquatic hemipterous insect of the genus Notonecta; -- so called from swimming on its back, which gives it the appearance of a little boat. Called also boat fly, {boat insect}, boatman, and water boatman. [1913 Webster]