1. To check the status, condition, or wellbeing of someone or something through an inspection or visit. We need to check up on grandma and see how she is coping with all this snow. I just checked up on the baby, and he's still sleeping. Can you check up on the dryer and tell me if it's still running?

2. To monitor what one is doing, especially when such attention is unwelcome or irritating to the one being monitored. Well, this work would go a lot faster if you quit checking up on me every five minutes!