bp,
As entertaining as the responses from the peanut gallery are to your legitimate question,

I can't find that there is a name for what you describe -- although "slamload" has a good ring to it, and echoes "slamfire" that occurs when the slide moves forward and fires a round in the process.
Here's a thread, one of many I am sure, about the issue in the M&P series. Long story short, it appears the manual will tell you not to insert the mag with substantial force, or the slide could move forward on its own.
thttp://smith-wessonforum.com/smith-wesson-m-p-pistols/204160-m-ps-auto-forward.html