That which fills a gap or hiatus.
A temporary measure or short-term fix used until something better can be obtained; that which serves as an expedient in an emergency; a band-aid solution.
The small company uses their old product with a few kludged enhancements as a stopgap until they can develop a new product.
Filling a gap or pause.
Temporary; short-term.
They put a stopgap solution in place, but need something more permanent.