FLU'ID, adjective [Latin fluidus, from fluo, to flow.] Having parts which easily move and change their relative position without separation, and which easily yield to pressure; that may flow; liquid. Water, spirit, air, are fluid substances. All bodies may be rendered fluid by heat or caloric.

FLU'ID, noun Any substance whose parts easily move and change their relative position without separation, and which yields to the slightest pressure; a substance which flows, or which moves spontaneously on a plane with the least inclination; a liquid; liquor; opposed to a solid. Water, blood, chyle, are fluids.