Pacer (noun)

1. A horse or other animal used to set the pace in a race.
2. A person or thing that sets the pace or rate of something.

Origin:

Derived from the verb "pace" which means "to move at a steady rate".

Examples:

1. The pacer horse was used to set the pace for the race.
2. The pacer helped the runners maintain their pace during the marathon.
3. The pacer was a crucial part of the training regimen for the track team.
4. The pacer was able to help the swimmers maintain their pace during the race.
5. The pacer helped the team stay on schedule.