[wait on] or [wait upon] {v.}
1. To serve.
* /Sue has a summer job waiting on an invalid./* /The clerk in the store asked if we had been waited upon./
2. {formal} To visit as a courtesy or for business.
* /We waited upon the widow out of respect for her husband./* /John waited upon the President with a letter of introduction./
3. To follow.
* /Success waits on hard work./