Y - Y shaped plumbing fitting.
Yard of Concrete - One cubic yard of concrete is 3'X 3'X 3'in volume, or 27 cubic feet; one cubic yard of concrete will pour 80 square feet of 3 ½" sidewalk or basement/garage floor.
Yoke - The location where a home's water meter is sometimes installed between two copper pipes, and located in the water meter pit in the yard.