The act of taking ones bowel movement and freezing it, then once frozen using it as a masterbatory aid.
Cold Merle is not limited to solid movements. A loose stool can be put into a condom then with the end being tied off, can then be frozen and also used for ones personal pleasure tool.
Other names include, stool tool, shit stick, poo sickle.
Janet loves a cold Merle on a hot summers day.