trainer Definition

1. Someone who trains racehorses, athletes, etc.

Thesaurus: coach, instructor, teacher, tutor.
(Brit)
2. Soft canvas or leather running shoes that have thick soles and no spikes, often worn just as casual shoes. N Amer equivalent sneaker.

Form: trainers
3. A machine or device used in training, eg an aircraft with two sets of controls for training pilots.
4. A piece of gym equipment such as a rowing machine, exercise bike, etc.