Definition of non compos mentis in US English:

non compos mentis

(also non compos)


  • Not sane or in one's right mind.

    • ‘Look, you are not the arbiter of what is or is not ‘pro-American’, you are just another rightist flamer who is non compos mentos.’
    • ‘There is nothing you can do without her consent - unless you were to challenge her mental capacity and prevail - so you have to respect her decision; either that or you must have her declared non compos.’
    • ‘The New York Times reports that several states are trying to establish the degree of mental impairment that would justify barring someone who is "non compos mentis"("not master of one's own mind") from casting a vote.’
    • ‘I heard his rant at the RNC and he struck me as non compos mentos.’
    • ‘He's had them ever since you were declared non compos.’
    mad, insane, mentally ill, certifiable, deranged, demented, of unsound mind, out of one's mind, not in one's right mind, sick in the head, not together, crazy, crazed, lunatic, unbalanced, unhinged, unstable, disturbed, distracted, stark mad, manic, frenzied, raving, distraught, frantic, hysterical, delirious, psychotic, psychopathic, mad as a hatter, mad as a march hare, away with the fairies, foaming at the mouth
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Latin, literally ‘not having control of one's mind’.


non compos mentis

/ˌnɑn ˌkɑmpəs ˈmɛn(t)əs//ˌnän ˌkämpəs ˈmen(t)əs/