(noun) an offhand term or casual reference for sleep. Usually used in the pejorative sense, suggesting sleep that will be nonexistent or minimal at best for the speaker.
Sleep, schmeep -- I don't have time to rest with the 50 projects due tomorrow.
A sunburn or suntan focused on the left arm. It is caused by the left side of the body being the only half that gets exposed to sunlight while driving. Presumably, it would be located on the right side of the body in countries where they drive on the left side of the road.