1. To be well in with someone - ie being in a relationship, or in someone's favour
2. Getting well in - can mean trying to start a relationship, pulling a bird, or getting to any of the 'bases' with anyone.
3."WELL IN!" as an exclamation - can be used either as an expression of success or celebration (ie an alternative to 'YES!') or used to indicate when a friend or associate is 'getting well in', usually in conjunction with a sharp elbow prod.
2. "Don't worry you're well in with my family, they like you."
3. "Dude shut up i'm tryin to get well in here!"
4. "Got well in last night...ahhhh!"
5. (Guy finishes a sudoku) "WELL IN!"
6. Friend A: (talking to girl on phone) "So...do you fancy coming to the cinema later? you know, just me and you? you would? awesome!"
Friend B: WELL IN LAD!!! (sharp elbow prod in the side)
Friend A: OW! feck off, loser! No, not you Charlotte!