fluid

noun

1. a substance, as a liquid or gas, that is capable of flowing and that changes its shape at a steady rate when acted upon by a force tending to change its shape.

adjective

2. pertaining to a substance that easily changes its shape; capable of flowing.
3. consisting of or pertaining to fluids.
4. changing readily; shifting; not fixed, stable, or rigid: fluid movements.
5. convertible into cash: fluid assets.

noun

1. a substance, such as a liquid or gas, that can flow, has no fixed shape, and offers little resistance to an external stress

adjective

2. capable of flowing and easily changing shape
3. of, concerned with, or using a fluid or fluids
4. constantly changing or apt to change
5. smooth in shape or movement; flowing

adj.

early 15c., from Middle French fluide (14c.) and directly from Latin fluidus “fluid, flowing, moist,” from fluere “to flow” (see fluent). Figurative use from 1640s. Related: Fluidly.

n.

1660s, from fluid (adj.).

n.

1. An amorphous substance whose molecules move freely past one another; a liquid or gas.

adj.

1. Of or characteristic of a fluid.

1. A state of matter, such as liquid or gas, in which the component particles (generally molecules) can move past one another. Fluids flow easily and conform to the shape of their containers. See also state of matter viscosity.

In physics, a substance that flows — usually a liquid or a gas.