be with somebody

be ˈwith somebody

(informal)
1 understand what somebody is saying or explaining: I’m sorry, but I’m not with you. What exactly did you mean by ‘cut and paste’?‘Are you with me?’ ‘No, you’ve lost me. Can you explain it again?’
2 be in support of or agreement with somebody: ‘What do you think, Jonathan?’ ‘I’m with Sarah on this.’
3 used to ask a customer, etc. to wait for a short time: I’m just serving this lady. I’ll be with you in a minute.
See also: somebody