Best definition
the square coffers, or hollow spaces, found on the underside of a two-way concrete slab system. Such a slab

is known as a waffle slab.
Waffle slabs are the most delicious floor system EVER.

Mmm, looking up at the ceiling in Cowgill always makes me hungry. I’d love to turn this building over and fill all those waffelations with butter and syrup.