What does the British term to skin up mean?

The British expression 'to skin up' refers to rolling a marijuana cigarette, also known as a joint. It involves placing marijuana or a similar substance inside a rolling paper, twisting the ends to seal it, and adding the necessary filter tip if desired. When rolled correctly, the marijuana cigarette can then be lit at one end and smoked.

This informal slang is commonly used amongst individuals engaged in recreational marijuana use within the United Kingdom. Please note that the legality surrounding marijuana varies based on regional laws and regulations.