chat up

from Wiktionary, Creative Commons Attribution/Share-Alike License.

• verb transitive, idiomatic To talk to (someone) in a friendly, open, or casual manner, sometimes also in a charming or affected manner, usually to curry favor, and sometimes flirtatiously with the intention of establishing a romantic or sexual encounter or relationship with that person.

from WordNet 3.0 Copyright 2006 by Princeton University. All rights reserved.

• verb talk to someone with the aim of persuading him
• verb talk or behave amorously, without serious intentions