/duy am"i teuhr/ , n.
1. Geom.
a. a straight line passing through the center of a circle or sphere and meeting the circumference or surface at each end.
b. a straight line passing from side to side of any figure or body, through its center.
2. the length of such a line.
3. the width of a circular or cylindrical object.
[ 1350-1400; ME diametre diametros diámetros diagonal, diameter, equiv. to dia- DIA- + -metros, deriv. of métron METER 1 ]