Rod Dynamics ?

Hello:

Was reading a book on ballistics the other day, and the author was
describing conditions
where a rifle barrel would drop a small amount as a shell was fired.

He used an example that if one held a fly rod rod truly horiz., and gave the
handle a very quick
upward (I think he means backwards; toward ones head) pure rotation, the tip
momentarily goes Downward.

Have my rods away for the season, so can't try it.

Can't visualize this happening.

Does it ?
Why does it, if so ?

B.