Mucus - a slippery, often colourless normal secretion or product of the lining to the colon which allows motions to slide through more easily. In certain conditions when the bowel is irritated, or even from piles, more mucous is produced and patients notice it either on or separate from the poo. It is very rarely a serious symptom unless it is associated with other changes in bowel function or rectal bleeding. Even then it is usually not anything serious.