noun
nincompoop; simpleton
A mildly derogatory term for a foolish or silly person; somewhat old-fashioned and not commonly used in modern conversation.
あいつはひょうろく玉だ。
That guy is a simpleton.
The origin is uncertain; the word may be derived from the sound-symbolic element ひょうろく, suggesting a clumsy or foolish person, combined with 玉 (だま, 'ball' or 'person'). The kanji spellings are ateji.