diameter (di-am'et-er)

The distance from any point on the periphery of a surface, body, or space to the opposite point. anterior transverse d. of the fetal head. See temporal d. anteroposterior d. of the pelvic cavity. The distance between the middle of the symphysis pubis and the upper border of the third sacral vertebra, anteroposterior d. of the pelvic inlet. The distance from the upper part of the symphysis pubis to the promontory of the sacrum. anteroposterior d. of the pelvic outlet. The distance from the lower part of the symphysis pubis to the tip of the coccyx. anteroposterior d. of the skull, anteroposterior metopic d. of the skull. The distance in a straight line between the metopic point and the most remote point upon the external surface of the tabular portion of the occipital bone, or between the most prominent point of the glabella and the most prominent point upon the external surface of the occipital bone, bas i lob regma tic d. The distance in a straight line between the basil on and the bregma.