Can anyone refute this definition of 'truth'?

Let's say we have a box with a slot in the top big enough for a quarter to fit. When we drop one in it comes out a hole in the bottom unimpeded. We conclude the box is empty. Must be true because it works right? But when we open the box we find there was ten dollars in quarters taped to the inside. It wasn't actually empty after all.
Truth turns out to be what actually is. Falsehood on the other hand would be what is not actual.

Your assumed "conclusion" is only "wrong" with respect to being a valid test for "emptiness".
(There is doubt in physics whether "emptiness" can be ultimately defined)

In the lingusitic literature you will find reference to Benjamin Lee Whorf, a one time fire investigator turned linguist, on account of his investigation of explosions caused by a cigarette thown into a dump of "empty" gasoline cans.

"What works" is always contextual and subject to revision. A "moving sun" works for gardeners but not for astronauts.

We cannot know the truth. We can only observe what works. Our functional lives dictate using what we perceive as “working” and cling to whatever hypothesis we have attached to that “truth”. This is all we can do, observe what seems to work and hopefully adopt new thinking for that which does not. It is quite likely that in all things we still find the truth of it outside our conception, but we can find functional methods for navigating our lives and achieving our goals. Since nearly all of our preoccupations are mental constructions with no consistent truth this should be more than adequate.

something can be pragmatic but untrue.
newton laws work to an extent but was disproven by einstein

http://asterisk.apod.com/wp/asow/2012/09/16/kepler-newton-and-einstein-wrong-theories-and-the-progress-of-science/