1)A Substitute Bus Driver.
The "bus" stands for the vehicle & the "titute" is short for Substitute which is a replacement for your original Bus Driver.
2)A Prostitute who frequents a city bus, school bus, or any type of elongated vehicle used to transport people from one distance to a designated area. The Bustitute, in this case, is often seen on the same bus once or several times a day on the same bus at the same time.
2) "That Bustitute is pissing me off with that awful smell of hers and the way she smokes. I might just kill her."