Definition of boatfly in English:

boatfly

noun

British
rare
  • A predatory water boatman of the genus Notonecta (family Notonectidae), which swims on its back using its long hind legs as oars.

Origin

Late 17th century; earliest use found in Nehemiah Grew (a1641–1712), botanist and physician. From boat + fly.

Pronunciation

boatfly

/ˈbəʊtflʌɪ/