Half-mash
A song that is built around--or relies so heavily on--a sample from another it might (or might as well) be considered a mashup of the new song and the sampled one.
"Pepper” by the Butthole Surfers samples “Loser” by Beck, and “Ice Ice Baby” by Vanilla Ice samples “Under Pressure” by Queen so much that each might as well be called a mashup, or at least a "half-mash."