Having particles which easily move and change their relative position without a separation of the mass, and which easily yield to pressure; capable of flowing; liquid or gaseous.(adjective)
source: webster1913
noun (n)
a substance that is fluid at room temperature and pressure(noun.substance)
source: wordnet30
continuous amorphous matter that tends to flow and to conform to the outline of its container: a liquid or a gas(noun.substance)
source: wordnet30
A fluid substance; a body whose particles move easily among themselves.(noun)
source: webster1913
adjective satellite (s)
subject to change; variable(adj.all)
Example: A fluid situation fraught with uncertainty.