insane Meaning, Definition & Usage

  1. adjective afflicted with or characteristic of mental derangement
    • was declared insane
    • insane laughter
  2. adjective satellite very foolish
    mad; harebrained.
    • harebrained ideas
    • took insane risks behind the wheel
    • a completely mad scheme to build a bridge between two mountains

WordNet

In*sane" adjective
Etymology
L. insanus. See In- not, and Sane.
Definitions
  1. Exhibiting unsoundness or disorded of mind; not sane; mad; deranged in mind; delirious; distracted. See Insanity, 2.
  2. Used by, or appropriated to, insane persons; as, an insane hospital.
  3. Causing insanity or madness. R.
    Or have we eaten on the insaneroot That takes the reason prisoner ? Shak.
  4. Characterized by insanity or the utmost folly; chimerical; unpractical; as, an insane plan, attempt, etc.
    I know not which was the insane measure. Southey.

Webster 1913