imaginary Meaning, Definition & Usage

  1. noun (mathematics) a number of the form a+bi where a and b are real numbers and i is the square root of -1
    complex number; complex quantity; imaginary number.
  2. adjective satellite not based on fact; unreal
    notional; fanciful.
    • the falsehood about some fanciful secret treaties"- F.D.Roosevelt
    • a small child's imaginary friends
    • to create a notional world for oneself

WordNet

Im*ag"i*na*ry adjective
Etymology
L. imaginarius: cf. F. imaginaire.
Definitions
  1. Existing only in imagination or fancy; not real; fancied; visionary; ideal.
    Wilt thou add to all the griefs I suffer Imaginary ills and fancied tortures? Addison.
    Syn. -- Ideal; fanciful; chimerical; visionary; fancied; unreal; illusive.
Im*ag"i*na*ry noun
Definitions
  1. (Alg.) An imaginary expression or quantity.

Webster 1913