More active, energetic, or responsive than is normal, expected, or healthy—such as an overactive imagination or thyroid.
Compound of 'over-' (Old English 'ofer') and 'active' (from Latin 'activus'). The prefix intensifies the meaning beyond normal levels.
Kids with 'overactive imaginations' are actually engaging more brain regions for creative thinking—so the condition that seems like a problem might be a neurological advantage!
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