spewin Share definition Flag Australian slang; vomiting, throwing up, etc. 2) bummed out. upset, regretful. I missed the big day yesterday mate cause I had to go out with nana. " aww yur spewin mate " " shitchyea" spewin by herbie January 22, 2004 0 0 Get merch Get the spewin mug. Buy Now — $32.95 See more merch