Pronunciation: (hel'pur), [key]
1. a person or thing that helps or gives assistance, support, etc.
2. an extra locomotive attached to a train at the front, middle, or rear, esp. to provide extra power for climbing a steep grade. Cf. doubleheader, pusher (def. 5).
Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease.