Wiktionary
root beer float
n. A dessert consisting of root beer poured over vanilla ice cream, so that the ice cream floats.
WordNet
root beer float
n. an ice-cream soda made with ice cream floating in root beer
Usage examples of "root beer float".
Michael leaned his shoulder against me and 'gazed longingly at my half-finished root beer float.
It took a few minutes to climb and line up correctly, moving in toward the waiting straw like a kid homing in on a root beer float in an old-fashioned ice cream shop.
As Myra slurped the last of the root beer float Ro gazed out the window at the blur of stars that rushed by at warp speed.
Or it could be going to the driving range and letting everyone hit a bucket of golf balls, and then going to a movie and finishing up with a root beer float at home.