noun, plural: haemorrhoids
(1) A type of portacaval anastomoses which forms between the superior rectal vein (of portal circulation) and the middle rectal veins and inferior rectal veins (of systemic circulation).
(2) A tumor, varix, or a venous swelling at or inside the anal sphincter.
They arise mainly due to portal hypertension. Constipation and diarrhea can lead to hemorrhoids when there is a heightened strain during bowel movements.
Word origin: Latin haemorrhoidae; from Greek haemo, 'blood', rhein, 'flow'