This is a sexuall act in which an obese man lays on top of a woman without holding himself up allowing all of his body weight to smother her, he then proceeds to fuck her while she fights for air. To complete the walrus you must make the necessary grunting noises similar to a walrus. Please note when finished you should check for signs of life.
Optional: This can also be done during anal, known as the reverse walrus, clapping like a walrus is also acceptable
"Did you hear what happened to Pam? She got the tim walrus and died of asphyxiation"