noun
1. : a horse entered in a race to set the pace for a horse of the same owner or stable that is being ridden to win
2. : a candidate running for a subordinate place on a ticket ; especially : the candidate for vice-president considered in relation to the candidate for president
3. : a staff officer's opposite on the line officers' promotion list with whose promotion the staff officer is advanced in grade on the same date
4. : a person frequently seen in close association with another : companion