1 : an apparatus used in distillation
2 : something that refines or transmutes as if by distillation
This was added for all those alchemists (pcs and npcs) whose lab the players visit. Oddly enough, I took chemistry in high school and college, and saw these in the lab. However, we never used one nor were we told what it was called. That said, when you look this up in your search engine of choice, you first get references to the ones used in making alcoholic drinks. So if you don’t have an alchemist, but do have a tavern that distills, you can talk about them there as well.