1. a person who manages, controls, or takes care of something or someone
2. a person who trains or works with animals, especially dogs
3. a person who deals with or processes something, such as luggage or cargo

Examples

• The dog handler trained the police dog to detect explosives.
• A baggage handler loads and unloads luggage at the airport.
• The event handler in the program responds when a user clicks a button.
• The horse handler has years of experience working with thoroughbreds.
• A crisis handler must remain calm under pressure.
• The luggage handler carefully placed the suitcases on the conveyor belt.