What does "butter up" mean?

To flatter, especially with the intent of personal gain.

What is a synonym for "butter up"?

Common synonyms include: brown-nose, butter, cajole, cajoling, coax, coax.

verb, slang

verb, slang ·Moderate ·College level

Verb

1
To flatter, especially with the intent of personal gain. figuratively, informal, transitive
"He takes every opportunity to butter up the boss."
2
flatter with the intention of getting something wordnet

"He takes every opportunity to butter up the boss."