(Science: anatomy, surgery) a varicose dilatation of a vein of the superior or inferior haemorrhoidal plexus, resulting from a persistent increase in venous pressure.
presents as a livid and painful swelling formed by the dilation of the blood vessels around the margin of, or within, the anus, from which blood or mucus is occasionally discharged.
The singular haemorrhoid is rarely used.
Origin: gr. Haimorrhois, L. Haemorrhoidae.