Pronunciation: (sub'grOOp"), [key]
1. a subordinate group; a division of a group.
2. Chem.a division of a group in the periodic table.
3. Math.a subset of a group that is closed under the group operation and in which every element has an inverse in the subset.
Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease.