Adjective intelligent has 4 senses
  1. intelligent - having the capacity for thought and reason especially to a high degree; "is there intelligent life in the universe?"; "an intelligent question"
    unintelligent, stupid, brainless, headless, feebleminded, half-witted, slow-witted, imbecile, imbecilic, idiotic, moronic
  2. intelligent, well-informed - possessing sound knowledge; "well-informed readers"
    Antonyms: naive, naif (indirect, via sophisticated)
  3. healthy, intelligent, levelheaded, sound - exercising or showing good judgment; "healthy scepticism"; "a healthy fear of rattlesnakes"; "the healthy attitude of French laws"; "healthy relations between labor and management"; "an intelligent solution"; "a sound approach to the problem"; "sound advice"; "no sound explanation for his decision"
    Antonym: unreasonable (indirect, via reasonable)
  4. intelligent, reasoning, thinking - endowed with the capacity to reason
    Antonym: irrational (indirect, via rational)