Noun has 2 senses

• fluidness(n = noun.attribute) fluidity, liquidity, liquidness, runniness - the property of flowing easily; "adding lead makes the alloy easier to cast because the melting point is reduced and the fluidity is increased"; "they believe that fluidity increases as the water gets warmer"

Derived form adjective fluid₂

• fluidness(n = noun.attribute) fluidity - a changeable quality; "a certain fluidness in his perception of time made him an unpredictable colleague"; "a charming Oriental fluidity of manner"; "demographers try to predict social fluidity"

Derived form adjective fluid₁