To eat outside. Combination of the words "Flay" and "Sil." Flay means food, and Sil means out.
Hey, John. We should go silflay.
From Richard Adam's book Watership Down - it's a word that's part of the rabbit language Lapine - it means to go above ground to eat.
I didn't silflay with the rest of the warren this morning - I'll go tonight.