The Monster Krabby Patty is a giant Krabby Patty sold at the Krusty Krab. The amount of meat in the patty is so great that most normal spatulas cannot flip it. A Monster Krabby Patty is a huge version of the Krabby Patty that is only seen in the episode "All That Glitters." Squidward says that no one has ordered a Monster Krabby Patty in ages. When SpongeBob tried to flip the patty, Spat was broken in half, and it was taken to the hospital. When Spat is cured, another fish/customer ordered a Monster Krabby Patty but Spat (SpongeBob’s Spatula) did not break, but instead SpongeBob's arm broke off.
Looks
It looks like a Krabby Patty, or any other burger, but it is huge. It is extremely unlikely that you could fit it in your own mouth. It's appearance looks almost like the character Meatwad from Aqua Teen Hunger Force.