39th base Share definition Flag When you get a girl to ride your dick in a movie theatre while your mom is down 2 to 5 rows, any more or less is just crazy, it also is easier to have a scitso monkey. dude my mom caught me attempting the 39th base yesterday.. 39th base by Duncsin July 7, 2008 0 0 Get merch Get the 39th base mug. Buy Now — $32.95 See more merch