'Pill bug' definitions:

Definition of 'pill bug'

From: WordNet
noun
Small terrestrial isopod with a convex segmented body that can roll up into a ball

Definition of 'Pill bug'

From: GCIDE
  • Pill \Pill\, n. [F. pilute, L. pilula a pill, little ball, dim. of L. pila a ball. Cf. Piles.]
  • 1. A medicine in the form of a little ball, or small round mass, to be swallowed whole. [1913 Webster]
  • 2. Figuratively, something offensive or nauseous which must be accepted or endured. --Udall. [1913 Webster]
  • Pill beetle (Zool.), any small beetle of the genus Byrrhus, having a rounded body, with the head concealed beneath the thorax.
  • Pill bug (Zool.), any terrestrial isopod of the genus Armadillo, having the habit of rolling itself into a ball when disturbed. Called also pill wood louse. [1913 Webster]