featherheaded

/ˈfɛðərˌhɛdɪd/
adjective
  1. Silly, foolish, or lacking good judgment; not serious or sensible.
    • His featherheaded plan to build a treehouse without any nails fell apart in the first rain.
    • The movie's featherheaded villain kept making ridiculous mistakes that made the audience laugh.
    • She dismissed his featherheaded comments about the stock market with a patient smile.