a stout darter, Etheostoma caeruleum, inhabiting the Great Lakes and Mississippi River drainages, the spawning male of which has the sides marked with oblique blue bars with red interspaces.
Origin of rainbow darter
An Americanism dating back to 1880–85
Also called soldierfish.
Dictionary.com Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2019