- use courage, reserve, nerve or strength to achieve something
- to visit someone for a short while
- ask someone to do something (officially)
- make an urgent request for somebody to do something
- ask someone in a group to speak
- He had to call on all his strength to get to the finals.
- We go past my sister’s house on the way home so let’s call on her.
- My neighbour is always handy if I need to call on her.
- Harry was called on to make a quick announcement at the meeting.
- The head of the church has called on the disgraced politician to resign.
- You can call on me if you need help with the garden.
- The manager called on all the staff to be mindful of the new budget restrictions.
- My maths teacher called on me for the answer, but I wasn’t listening and got in trouble.
- Catherine needed to call on all her courage to stand up to the office bully.
- The government is calling on our allies to reach an agreement.
This is a phrasal verb with several uses as above. You can also use call upon.