/ sɜːˈfæktənt; NAmE sɜːrˈf-/ noun [ C , U ]
1.
( technical ) a substance that reduces the surface tension of a liquid, often forming bubbles in the liquid
2.
( medical ) a substance that keeps the lungs working well to prevent breathing problems
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WORD ORIGIN
1950s: from surf(ace)-act(ive) + -ant .