Hardened sap from trees which is used on violin bows, Bull Rider and Baseball gloves, bottoms of pointe shoes, etc. Helps retain a good grip on something, makes it not so slippery.
Dancer 1 : "Yesterday I was dancing in pointe class...and I slipped and fell on my butt..it was extremely embarrassing."
Dancer 2: "Did you get rosin from the rosin box?"
Dancer 1: "Oops, no."
Dancer 2: "Well that explains it."
Stems from an anonumous post-secret "You're cozy, Rosin", created for Canadian rock band Hedley's epic guitarist Dave Rosin. Rosin is famous for being exceptionally friendly and remembering fans' names and details about how he met them.
I need a rosin hug.