- to flatter someone so as to get something in return from them
- to say nice things excessively to someone just so they can do you a favour
- to charm someone with praise or compliments because you need something from them
- Mary's nice compliments about her not so nice boss made it clear that she was just trying to butter him up.
- Buttering up people is a good way to get them to help you when you need it.
- Alice is good at buttering up her superiors and that's how she mostly gets promoted.
- I am not so good at buttering up people just because I can be quite direct and blunt.
- John's offhand remarks about his boss showed that his previous compliments only served to butter his boss up.
- To butter up people is really not the best way to get them to be kind to you
This phrase derives directly from the act of spreading butter on bread or any other edible substance to make it soft and tastier so that the person eating it gets more satisfaction from it. So this came to represent spreading nice things about someone just so you could get something in return.