Biggest Of All Time in referring to a shit. Poop that looks not only inhumanly possible, but also makes you want to show everyone in the house. Nautical references also apply, as it looks like you just shit a yacht.
Me: "omg Mom, come look at this poop!"
Mom: "son you just shit a B.O.A.T."
"That shit was literally the biggest of all time"
Mom: "son you just shit a B.O.A.T."
"That shit was literally the biggest of all time"
by Captain Ish August 13, 2009