fi·lum ter·mi·na·le 'fī-ləm-.tər-mə-'nā-(.)lē, 'fē-ləm-.ter-mə-'näl-.ā n, pl fi·la ter·mi·na·lia 'fī-lə-tər-mə-'nā-lē-ə, 'fē-lə-.ter-mə-'näl-ē-ə the slender threadlike prolongation of the spinal cord below the origin of the lumbar nerves: the last portion of the pia mater
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[TA] terminal filum: a slender threadlike filament of connective tissue that descends from the conus medullaris to attach to the inner aspect of the dural sac and from there to the base of the coccyx; divided into a pial part (pars pialis fili terminalis) and a dural part (pars duralis fili terminalis), the dividing line being the lower border of the second sacral vertebra.Medical dictionary. 2011.