: to gain or regain the favor or goodwill of : appease, conciliate
In other words: to kiss ass.
Merriam Webster's "formal" definition of kiss ass is : [usually vulgar] to act obsequiously especially to gain favor. The idiom section of The Free Dictionary elaborates with: to praise someone more than is reasonable, usually said about praise intended to make someone like you or do something you want. In a witty and informative article about the word ass as a suffix, kiss ass is defined as : to flatter someone or attempt to ingratiate one's self.
Other informal synonyms for PROPITIATE: brownnose, suck up, bootlick, scratch one's back, cajole, sweet-talk, butter-up, and—my favorite—apple-polish, a bi-product of the acts of good little children who bring their school teachers shiny red apples.
Which I never did. It was pretty old-fashioned by the time the eighties rolled around. I mean, I watched Nick-at-Night, I didn't live it.
By the way, do not conduct a google search for "apple teacher suck up" if you are of the faint of heart.