Stored in, shaped like, or having the form of a barrel; cylindrical.
From barrel plus -ed, the past participle suffix that can create adjectives meaning 'having' or 'provided with' something, as in 'talented' or 'bearded.'
Barrelled chests in medical terminology describe an unusually rounded chest shape—when you hear this in a doctor's office, it usually indicates chronic lung disease because the lungs have overinflated the ribcage.
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