Definition of arachnoid in English:



  • Like a spider or arachnid.

    • ‘Results-wise, it's difficult to extrapolate from inferred arachnoid motivations to the human mental-state.’
    • ‘Watching the erstwhile nerd get used to his muscular new body and powers - accidentally firing off webs and finding things sticking to his arachnoid hands - is one of the most engaging parts of the film.’
    • ‘Their words paralyze me like the bite of an arachnoid.’
    • ‘Oddly enough, if I know for certain that the scuttling thing isn't arachnoid in nature, it doesn't bother me in the slightest.’
    • ‘The filmmakers really rushed the transition to arachnoid too quickly.’


  • A fine, delicate membrane, the middle one of the three membranes or meninges that surround the brain and spinal cord, situated between the dura mater and the pia mater.

    • ‘Between the pia and arachnoid membranes is the subarachnoid space, in which the cerebrospinal fluid circulates.’
    • ‘The surgeon opens the arachnoid membrane dorsal to the seventh and eighth nerves and continues the opening upward to the fourth nerve.’
    • ‘The lining consists of three layers - dura, arachnoid and pia.’


Mid 18th century: from modern Latin arachnoides, from Greek arakhnoeidēs like a cobweb from arakhnē spider.