not clear or bright; slow to understand; not exciting or interesting

unintelligent

foolish (and showing self-importance)

stupid

without reason, sense or good judgement; silly

nonsensical, idiotic

causing, having, the feeling that everything is turning round so that one cannot stand steady

silly, impulsive

without the power to reason; absurd, not reasonable

illogical, senseless

not sensible; foolish

absurd, giddy, foolish

unintelligent; foolish

not intelligent; irresponsible