What does "shoot down" mean?

Ruin the aspirations of, disappoint, as in Bill was hoping Sharon would go out with him, but she shot him down.

Reject, defeat; also, expose as false. For example, It was the best idea I could come up with, but they unanimously shot it down, or It was inevitable that they would shoot down any claim made by the opposing candidate. This colloquial expression, which alludes to bringing down an aircraft or game bird by shooting, is sometimes intensified as shoot down in flames, originally (in World War I) referring to bringing down enemy aircraft but the late 1950s extended to decisively defeating anyone or anything.