pill bug

noun

any of various small terrestrial isopods, especially of the genera Armadillidium and Oniscus, which can roll themselves up into a spherical shape.

Origin of pill bug

An Americanism dating back to 1835–45

Dictionary.com Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2018

British Dictionary definitions for pillbug

pill bug

noun

any of various woodlice of the genera Armadillidium and Oniscus, capable of rolling up into a ball when disturbed

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

Word Origin and History for pillbug

also pill-bug, 1841, from pill (n.) + bug (n.).