Noun
sycophant (plural sycophants)

1. One who uses obsequious compliments to gain self-serving favour or advantage from another; a servile flatterer.
   Synonyms: ass-kisser, brown noser, suck-up, yes man
2. One who seeks to gain through the powerful and influential.
   Synonyms: parasite, flunky, lackey
3. (obsolete) An informer; a talebearer.

Derived terms:
sycophancy
sycophantic
sycophantish
sycophantism

Verb
sycophant (third-person singular simple present sycophants, present participle sycophanting, simple past and past participle sycophanted)

1. (transitive, obsolete) To inform against; hence, to calumniate.
2. (transitive, rare) To play the sycophant toward; to flatter obsequiously.