Pronunciation: (pen"ē-roi'ul), [key]
1. an aromatic Old World plant, Mentha pulegium, of the mint family, having clusters of small purple flowers and yielding a pungent essential oil used medicinally and as an insect repellent.
2. Also called mock pennyroyal. a similar, related plant, Hedeoma pulegioides, of eastern North America, having bluish flowers growing from the leaf axils.
3. any of several other aromatic plants of the mint family.
Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease.