Definitions of fluid:

• noun:   a continuous amorphous substance that tends to flow and to conform to the outline of its container: a liquid or a gas
• noun:   a substance that is fluid at room temperature and pressure
• adjective:   characteristic of a fluid; capable of flowing and easily changing shape
• adjective:   subject to change; variable

  Example: "A fluid situation fraught with uncertainty"

• adjective:   affording change (especially in social status)

  Example: "Britain is not a truly fluid society"

• adjective:   in cash or easily convertible to cash

  Example: "Liquid (or fluid) assets"

• adjective:   smooth and unconstrained in movement

  Example: "The fluid motion of a cat"