Blackhead

[Little_Girl]

Dirty sebacious matter [clogging] a [pore] to the point it is visible to others. Most often found on noses, cheeks and [chins], though they can develop anywhere. They are often satisfying to squeeze. They are also a sign the person does not take very good care of him- or herself.

[Dave Paprocki]

A plug of sebum in a hair follicle, darkened by oxidation.