A fudge is an inelegant or clumsy solution to a problem. Usually a quick fix, will more often than not come back to haunt you if you don’t fix it properly later, and almost always not supported by the manufacturer. The occasional ‘dirty fudge’ or superlative ‘filthy fudge’ are indications of the extremity of the inelegance.
May also be used as a verb:
“The licence activation doesn’t work properly, so I fudged it instead.”