Rocky Mountain locust
a migratory locust, Melanoplus spretus, that occurs in North America, especially the Great Plains, where swarms cause great damage to crops and other vegetation.
Origin of Rocky Mountain locust
An Americanism dating back to 1875–80
Also called Rocky Mountain grasshopper.
Dictionary.com Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2019