Other forms: underfunded; underfunding; underfunds
To underfund is to provide an insufficient amount of money for something. If a school district underfunds its art program, there won't be enough paint, clay, and other materials to go around.
To fund a project or organization is to provide the money needed to start it or keep it running. Underfund means to supply some cash, but not enough. If your parents offer to pay for your European trip but then underfund it, you may find yourself sleeping on overnight trains and eating baguettes and cheese for lunch and dinner. Still not a bad way to spend a week!