Kiss somebody’s arse
Definition 1 of 1
Pro Tip 1/3Informal Usage
The phrase is informal and often considered rude or disrespectful if used directly. 
I wouldn't say he's kissing anyone's arse; that's quite a harsh thing to say.
Pro Tip 2/3Negative Connotation
It carries a negative view of someone's behavior, suggesting dishonesty or insincerity. 
Everyone knows she didn't mean that compliment; she's just kissing her manager's arse.
Pro Tip 3/3Personal Benefit
Implies the act is done for personal gain, like a job or favor. 
He's not really that nice; he's just kissing your arse for a free ride.