1. Literally, to hit, kick, or knock someone or something on some specific location. In this usage, a noun or pronoun is used between "strike" and "upon." The child struck her dad on the head with the toy hammer.

2. To make a sudden or unexpected discovery. We've struck upon a new way to treat cancer as a result of our research into immune system modification. It appears the film studio has struck upon a winning formula with its recent blockbuster series.

3. To highlight, introduce, or raise some topic or issue. I think you've struck on an important point, Jim. The CEO struck on a number of key figures during his presentation to investors.