1. Work for, or be a servant to
   "May I wait upon you?";
   - serve, attend to, wait on, attend, assist
    
2. Depend on or be contingent on
   "The decision will wait upon the outcome of the vote";
   - wait on
    
3. Await or anticipate eagerly
   "We're waiting upon the results";
   - wait on

Derived forms: waited upon, waits upon, waiting upon

Type of: aid, assist, help