Originally a wrestling expression that has worked its way into American politics and will no doubt end up being adopted by business because in the USA they love their sporting metaphors.
It means to shut someone up by making them look stupid.
It is normally proclaimed by one of the on lookers if they believe the put down is worthy of recognition.
It is a pulling together of two words
"smack" and "down" popularised by WWE wrestler-turned-actor The Rock to describe a an emphatic winning move.
The newly elected mayor of New York Bill de Blasio celebrated his emphatic victory when his family joined him on stage for the now famous "Smackdown" dance.
Can we expect to hear "Smackdowns" proclaimed in the trendier management meetings over here in the New Year? The dance may be a step too far for the more conservative board members but then again who would have thought " high five" would have made it beyond the sports field.