A
nodeshell for such a cool word?
Egad. Well. (
/me rolls up sleeves) a
surfactant is a substance that, when
dissolved into or mixed with a liquid (typically
water) has the effect of lessening the
surface tension of the target fluid. The most common use of such a substance is
soap, which is a surfactant and used to not only dissolve
greasy liquids but to increase the 'wetness' of water.
If you're a car buff, there are products designed to do this in your radiator coolant. The point is to reduce the size of bubbles formed in the coolant (because the bubbles interfere with heat transfer, the radiator's job) and to ensure the coolant contacts all of the heat exchange surface. One popular brand is named, aptly enough, Water Wetter.
According to Princeton's online dictionary, the name was produced as follows:
surface plus active plus agent