godan verb (-ru), intransitive verb
be arrogant; be proud; be haughty; show off
Describes a person acting superior or boastful, often with a negative connotation. Commonly used in the set phrase 驕る平家は久しからず (the proud Heike do not last long).
彼は成功してからすっかりおごってしまった。
He became completely arrogant after his success.
Don't get cocky; there's still a long way to go.