D defs.my
Entry 2 senses Webster, 1913

Perimeter

/pẽr-ĭm'-ət-ẽr/ · Per·im·e·ter · IPA /[pəˈɹɪm.ɪ.ɾɚ]/
01 n. The outer boundary of a body or figure, or the sum of all the sides.
  1. 1.
    The outer boundary of a body or figure, or the sum of all the sides.(Geom.)
  2. 2.
    An instrument for determining the extent and shape of the field of vision.