yeahup Share definition Flag A word, combining 'yeah' and 'yup'. It is just a fun word to say. Pronounced: yeah-up. "Are you going to the cinema on Friday?" asked Michelle. "Yeahup," answered Clare. yeahup by Tricia Marie August 4, 2007 0 0 Get merch Get the yeahup mug. Buy Now — $32.95 See more merch