A substance that reduces or eliminates foam; an additive used to remove or prevent foam formation.
From defoam + -er (agent noun suffix). The -er suffix transforms a verb into a noun for either the person doing the action or (in this case) the substance or device that does it.
Anti-foaming agents are fascinating chemical compounds—silicone-based defoamers are among the most effective, and they work by breaking the surface tension of bubbles, a principle so useful that defoamers appear in almost every major industrial process from food to pharmaceuticals.
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