Having had foam removed; having been treated to eliminate or reduce foam.
Past participle of defoam, combining de- + foam + -ed. The -ed suffix marks the completed action or resulting state.
The passive voice 'defoamed' appears often in technical specifications—'defoamed oil' or 'defoamed latex' tells manufacturers that they're getting material that's been processed to remove unwanted bubbles, a quality that affects how the substance will perform.
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