comedo(n = noun.body) blackhead - a black-tipped plug clogging a pore of the skin;
is a kind of blemish, defect, mar
is a part of cutis, skin, tegument

   A small nodule or cystic tumor, common on the nose, etc., which on pressure allows the escape of a yellow wormlike mass of retained oily secretion, with a black head (dirt). [1913 Webster]

comedo, n. (pl. comedones) Med. a blackhead.

Etymology:
L, = glutton f. comedere eat up