A person, typically a man, who serves food and drinks to customers in a restaurant. The waiter took our order and brought us our drinks promptly.
Archaic. A person who waits or stays in expectation of something or someone. A solitary waiter by the roadside hoped in vain for a passing carriage.
Computing. A program or routine that remains in a dormant state until it is triggered by an external event. The file-system waiter monitors the directory and activates when a new file appears.