starter

Concise Oxford English Dictionary © 2008 Oxford University Press:
starter/ˈstɑːtə(r)/

▶noun

• 1 a person or thing starting in a specified way: a slow starter.

  ■ a person who signals the start of a race.

  ■ a competitor taking part in a race or game at the start.

  ■ Baseball the pitcher who starts the game.

• 2 an automatic device for starting a machine.

  ■ a railway signal controlling the starting of trains.

• 3 chiefly Brit. the first course of a meal.

• 4 a topic or question with which to start a discussion or course of study.

• 5 a preparation used to initiate souring, fermentation, etc.

– phrases
for starters informal first of all.
under starter's orders (of horses, runners, etc.) waiting for the signal to start a race.