'boat insect' definitions:

Definition of 'boat insect'

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]