A genuine issue of material fact is a disagreement between opposing parties on facts legally relevant to a claim. The disagreement must be "genuine" in the sense that it must be plausible (e.g., one cannot logically dispute a contract date without also alleging that a copy of a contract with that date inaccurately reflects the agreement).
A genuine issue of material fact precludes summary judgment, since a summary judgment is proper if there is no genuine issue of material fact and the movant is entitled to a judgment as a matter of law. The burden of proof shifts to the nonmoving party when the moving party makes a prima facie showing that there isn't a genuine issue over a material fact, this showing must be refuted by the nonmoving party by providing substantial evidence raising a genuine issue over a material fact.
[Last updated in January of 2023 by the Wex Definitions Team]