Flatter is a comparative adjective of a word "FLAT" and also a verb.
1. Lavish praise and compliments on (someone), often insincerely and with the aim of furthering one's own interests.
1. Having a level surface; without raised areas or indentations.
Verb forms: Flatter, Flattered, Flattered.
1. Don't flatter yourself! I wasn't doing it for your benefit!
2. The river has a flatter bottom.