Noun. The act of male masturbation; a jerk-off. Generally used within the phrase "have a mastie" or "having a mastie"

when you're hungover as shit after a spending a night drunk as a skunk

A word used by the chronically ill and/or invisible illness community to refer to people who are diagnosed with a mast cell disorder - generally either Mast Cell Activation Syndrome (MCAS) or mastocytosis. "Mastie" is a cute name to refer to the person diagnosed with the condition. It's shortened for easier usage.

A person who has a mast cell disorder