What does it mean if a summary judgement was reversed?

At a minimum, it means exactly what it sounds like--that there had been a judgment for one party, granted on a motion for summary judgment, which judgment has now been undone, whether on application for reconsideration to the same court or on an appeal to a higher (e.g. appellate) court. What else it means depends on what order was made by the court reversing the summary judgment--the most common outcome is that the case either goes forward towards trial (if the judgment was reversed by the trial court itself, such as on a motion for reconsideration), or is remanded (sent back to) the trial court for trial (if reversed on appeal). However, you need to review the court order to see exactly what it provides for.