noun, plural: sebaceous glands
A sebaceous gland is an exocrine gland in the skin that secretes sebum usually into a hair follicle near the surface of the skin. The sebum it secretes is essential in lubricating the hair and the skin. It is an oily substance that gives skin and hair its waterproof characteristic.
A specialized sebaceous gland in the eyelids is called meibomian gland. It is found in the tarsal plate in the eyelid and secretes an oily substance, specifically referred to as meibum oil. The meibum oil is a type of sebum that serves as a hydrophobic barrier to help prevent tears from readily spilling onto the cheek and from evaporation of the tear film in the eye.