ETYM Latin fluidus, from fluere to flow: cf. French fluide. Related to Fluent.
Any substance, either liquid or gas, in which the molecules are relatively mobile and can 'flow'.
1. Characteristic of a fluid; capable of flowing and easily changing shape; SYN. runny.
2. Subject to change; variable; SYN. unstable.
3. Affording change (especially in social status); SYN. mobile.
4. In cash or easily convertible to cash; SYN. liquid.

1. A continuous amorphous substance that tends to flow and to conform to the outline of its container: a liquid or a gas.
2. A substance that is fluid at room temperature and pressure.