arrowworm

[ar-oh-wurm]

noun

any small, translucent marine worm of the phylum (or class) Chaetognatha, having lateral and caudal fins.

Origin of arrowworm

First recorded in 1885–90; so called from a fancied resemblance to an arrow
Also called glassworm.
Dictionary.com Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2019

British Dictionary definitions for arrowworm

arrowworm

noun

any small marine invertebrate of the genus Sagitta, having an elongated transparent body with fins and prehensile oral bristles: phylum Chaetognatha (chaetognaths)
Collins English Dictionary - Complete & Unabridged 2012 Digital Edition © William Collins Sons & Co. Ltd. 1979, 1986 © HarperCollins Publishers 1998, 2000, 2003, 2005, 2006, 2007, 2009, 2012