The essence of a person that is being deceptive, or the act of being deceptive. AKA trying to pull the wool over someones eyes.
Mom says, "Did you do your homework?"
Son says, "Yes Mom."
(When in fact he did not...)
Mom says, "Son- stop being deceptious."
An extremely, underhanded, deceitful action, thought, idea, belief, value etc.
Deceptious in his thinking as he sought to hide the papers he had recently removed from his fathers briefcase.