Derm can refer to different things depending on the context. Here are some definitions:

• Dermatology: Derm is an abbreviation for dermatology, which is the branch of medicine that deals with the skin and its diseases.
• Skin: Derm can also be a combining form that means skin.
• Chinese festival: In American English, derm can refer to a Chinese festival that celebrates the end of the summer harvest.
• Navigational device: In some contexts, derm can refer to a navigational device used to make a nearby object visible on a radarscope.
• Slang for dermatologist: In slang, derm can be a clipping of dermatologist.
• Intestine or gut: In Afrikaans, derm can mean intestine or gut.

So, the meaning of derm depends on the context in which it is used.