pe·rim·e·ter / pəˈrimitər/ • n. 1. the continuous line forming the boundary of a closed geometric figure: the perimeter of a rectangle. ∎  the length of such a line: the rectangle has a perimeter of 30 cm. ∎  the outermost parts or boundary of an area or object: the perimeter of the garden| fig. my presence on the perimeter of his life. ∎  a defended boundary of a military position or base. ∎  Basketball an area away from the basket, beyond the reach of the defensive team: he was very patient in working the ball around the perimeter.2. an instrument for measuring the extent and characteristics of a person's field of vision.DERIVATIVES: per·i·met·ric / ˌperəˈmetrik/ adj.

cir·cum·fer·ence / sərˈkəmf(ə)rəns/ (abbr.: cir., circ., or circum.) • n. the enclosing boundary of a curved geometric figure, esp. a circle. ∎  the distance around something. ∎  the edge or region that entirely surrounds something: petals on the circumference are larger than those in the center.DERIVATIVES: cir·cum·fer·en·tial / sərˌkəmfəˈrenchəl/ adj.cir·cum·fer·en·tial·ly adv.

perimeter XVI. — F. périmètre — L. perimetros — Gr. perímetros, f. PERI- + métron METRE1.

perimeter (per-im-it-er) n. an instrument for mapping the absolute extent of the visual field and detecting any gaps or defects.
—perimetry n.