sebaceous gland vs oil gland

sebaceous gland and oil gland both are nouns.

Word	Noun	Adjective	Verb	Adverb
sebaceous gland	Yes	No	No	No
oil gland	Yes	No	No	No

As nouns, oil gland is a hypernym of sebaceous gland; that is, oil gland is a word with a broader meaning than sebaceous gland:

sebaceous gland: a cutaneous gland that secretes sebum (usually into a hair follicle) for lubricating hair and skin
oil gland: a gland that secretes oil

sebaceous gland (noun)	oil gland (noun)
a cutaneous gland that secretes sebum (usually into a hair follicle) for lubricating hair and skin	a gland that secretes oil