cattle prod

American Heritage® Dictionary of the English Language, Fourth Edition

1. n. A usually electrified prod designed for driving cattle.

Wiktionary

1. n. A stick designed to goad cows, steers, and similar animals in order to prompt them to move in a desired direction, now usually electrified to administer a stimulating shock to the animal.
2. n. figuratively Something used to goad or push someone to act.