fluid in WordNet English dictionary

1. smooth and unconstrained in movement
   "a long, smooth stride"; "the fluid motion of a cat"; "the liquid grace of a ballerina"
   fluent  fluid  liquid  smooth 
   
2. subject to change; variable
   "a fluid situation fraught with uncertainty"; "everything was unstable following the coup"
   fluid  unstable 
   
3. in cash or easily convertible to cash
   "liquid (or fluid) assets"
   fluid  liquid 
   
4. characteristic of a fluid; capable of flowing and easily changing shape
   fluid  runny 
   
5. affording change (especially in social status)
   "Britain is not a truly fluid society"; "upwardly mobile"
   fluid  mobile 
   

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