trainer

noun

1. A person who trains another; a coach.

   “It was [Roger] Federer’s ability to pull him around the court that put the lactic acid and debilitating weight in those legs and he should not have been allowed the luxury of his trainer’s help.”

2. A person responsible for treating injuries sustained by players during matches; a physiotherapist.

   “He served Nelson wholeheartedly as a player, coach and trainer in a lengthy association, the highlights being his involvement in two championship-winning sides.”

3. (Ireland, UK)A running shoe or sneaker.
4. (slang)A patch for a video game that applies cheats.

   “I actually never got a trainer for RCT, but needed one for my brother when I installed it on his computer. He is 10, and is only concerned with making "cool" coasters. I also completed CF before getting trainers.”

   “Are there any sites that have original copies of games? (ie: Summer/Winter/World Games with Fast Loading). Just looking for games without the trainers/intros.”

5. A piece of indoor equipment allowing a bicycle to be ridden while stationary.
6. A device for encouraging the roots of a plant to grow in a certain direction.

   “a root trainer”

7. (attributive, form-of)Attributive form of trainers.

   “There was chewing gum stuck to my trainer soles.”