Definition of "single-acting" [sin•gle-act•ing]

• Having simplicity of action; especially acting or exerting force during strokes in one direction only; said of a reciprocating engine, pump, etc. (adjective)

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• "Baking powder is available as single-acting baking powder and as double-acting baking powder."
• "Or make your own homemade single-acting baking powder."
• "For this cake, Miss Lewis called for 4 teaspoons of a particular single-acting baking powder called Royal Baking Powder."