musclehead; gym rat; person obsessed with building muscle
Colloquial, often mildly derogatory term for someone who prioritizes muscle training above all else, sometimes implying a lack of intellectual pursuits.
He's a musclehead who spends all day at the gym.
People call me a gym rat, but I do it for my health.
脳筋 is a similar slang term literally meaning 'brain muscle,' implying someone who solves everything with brute force or physical effort, while 筋肉バカ focuses more on the obsession with bodybuilding.
Common colloquial spelling using katakana for バカ.
Kanji spelling for 馬鹿; less common in this compound.
Compound of 筋肉 (muscle) and バカ (fool). The exact origin is uncertain, but it likely arose as casual slang to describe someone excessively devoted to muscle training.