Lateseff Share definition Flag Someone who is continually late to every event. This can sometimes lead to even "dogging" the event. Hammy is 30 minutes late for gym, what a fuckin lateseff. He might not even show up. Lateseff by TheRealMiffyRabbit August 21, 2013 0 0 Get merch Get the Lateseff mug. Buy Now — $32.95 See more merch