Molly

It refers to a substance that is packed into a gelcap which is a capsule shaped tablet coated with gelatin. In fact the substance should be MDMA (synthetic drug) inside the gelcap but mostly you will come across substances like methylone, BZP, a benzofuran, talc, or something more toxic like PMA. Make sure you taste it before consuming. https://dancesafe.org/testing-kit-instructions/ is a good resource.