not capable of being precisely or readily described; not easily put into words; "an indefinable feeling of terror"; "an abstract concept that seems indefinable"
defying expression or description; "indefinable yearnings"; "indescribable beauty"; "ineffable ecstasy"; "inexpressible anguish"; "unspeakable happiness"; "unutterable contempt"; "a thing of untellable splendor"
the quality of lacking any predictable order or plan
(thermodynamics) a thermodynamic quantity representing the amount of energy in a system that is no longer available for doing mechanical work; "entropy increases as matter and energy in the universe degrade to an ultimate state of inert uniformity"
ready and able to resort to force or violence; "pugnacious spirits...lamented that there was so little prospect of an exhilarating disturbance"- Herman Melville; "they were rough and determined fighting men"