purely imaginary; entirely unreal; fanciful; impossible to grasp

A philosophical viewpoint that suggests life is without objective meaning or value; the rejection of all religious and moral principles, often in the belief that life is meaningless.

(variant form) illusory, vague, and with no substance; unreal like a dream or mist

(variant form) empty and unreal; imaginary or purely visionary

null hypothesis in statistics; the assumption that there is no significant difference between specified populations