n.
a substance that has no fixed shape and yields easily to external pressure; a gas or (especially) a liquid.
adj.
- able to flow easily.
- not settled or stable.
- smoothly elegant or graceful.
- (of a clutch or coupling) using a liquid to transmit power.
Derivative
Etymology
ME (as adj.): from Fr. fluide or L. fluidus, from fluere ‘to flow’.