weigh somebody/something ↔ up phrasal verb ( see also ↑ weigh )
1 . to consider something carefully so that you can make a decision about it:
We’re still weighing up the pros and cons (=the advantages and disadvantages) of the two options.
2 . to watch someone and listen to them carefully so that you can form an opinion about what they are like:
I could see that he was weighing me up.