Extremely good, wonderful, impressive, or revolutionary, often said facetiously or sarcastically. Taken from the more common expression "the best thing since sliced bread." In this usage, a pan, in which a loaf of bread is baked, refers to the loaf of bread itself. Primarily heard in Ireland. I don't care what you say, I think she's the best thing since sliced pan! This new smartphone design really is the best thing since sliced pan.