sewer whale Share definition Flag A peice excrement so large that after the flush the tail is still visible in the shitter. Dude, after all the booze and early morning waffles i dropped a sewer whale. The plumber should be here any minute. Call the EPA... sewer whale by Asa Guy May 15, 2007 0 0 Get merch Get the sewer whale mug. Buy Now — $32.95 See more merch