di·am·e·ter /daɪˈæmɪtə(r)/ n. 1. 直径，对径，径 The circle has a diameter of 6 inches. 这圆直径6英寸。 How wide is the tyre in diameter? 这轮胎直径有多少? 2. (透镜的)放大倍数，放大率 a microscope magnifying 60 diameters 放大60倍的显微镜 [< ML diametrus < L diametros < Gr: diameter, diagonal < DIA- + metron measure]