2.VerbTo select (a student in a classroom, etc.) to provide an answer.
"He sat there, baffled, hoping nobody would call on him."
3.VerbTo request or ask something of (a person); to select for a task.
"The king called on his subjects to take up arms and defend the kingdom."
4.VerbTo have recourse to.
"Exhausted, he called on his last ounce of strength.; The young adventurer set out on the new planet alone, thankful that she could still call on her captain for advice in case of emergency."
5.VerbTo correct; to point out an error or untruth.
"The salesman persisted in quoting a rate higher than was listed, until we called him on it."