What is a catch?

[cinci4life]

In the MSU/OSU game the MSU receiver came back to the ball and appeared to catch the ball met by the defender about the same time then both go down with the receiver on top of the defender and not down on the ground. He reached the ball to the first down line while the defender got his hand up and knocked it loose before the elbow hit to make him officially down. OSU had an immediate recovery but the receiver was ruled to be down. They reviewed it with replay showing what appeared to be a clear catch, fumble and OSU recovery but it was ruled an incomplete catch. Gave me flashbacks to the OSU/Clemson playoff game when OSU was screwed out of a fumble 6. NFL or NCAA it doesn't seem like anyone knows what a catch is anymore.