pick up on someone—
1. (Racing ) draw near a person; begin to overtake a competitor:
- Benedict, knowing that he had the fastest car, was inclined to allow Chalmers to pick up on him….
2. (U.S. coll.) understand or appreciate a person:
- After Baudelaire picked up on him, Edgar Allen Poe had enormous influence on French literature and art.
pick up with someone—enter into conversation and make acquaintance with smb. casually met:
- So you’ve let your Polly go and pick up with some young man from town.
Note: Neither expression correlates in meaning with the phrase pick someone up—
1. take a person along with one, into one’s company or into a vehicle (collecting him from a place):
- I remember picking him up from work that night to take him home (he had no car).
2. form an acquaintance with a person casually or informally, especially with the intention of having a sexual relationship:
- She wished she had not picked Markie up in the train and given him her address.
3. (coll.) find fault with a person; call smb. to account:
- I am picked up for saying that the initiative in the Steamer case should have come from the stewards.
4. (sl.) rob, cheat, or swindle a person:
- There are loose characters lurking about, on the look-out for strangers, to “pick them up,” as they term it, which, in other words, means to rob them.
5. cause a person to revitalize; serve as a “pick-meup”:
- Have you had your tea? A cup of tea will pick you up.
6. (sl.) arrest or apprehend a person:
- Things start to go badly for him. His boys … get picked up for every minor charge in the book.