"Smooth move" is a sarcastic comment in response to a stupid or crass action and "exlax" is a pejorative reference to the perpetrator of such action. The whole term comes, of course, from the fact that Exlax enables smooth bowel movements.

The insulting capability of "smooth move exlax" runs the gamut from a mild put down (as to an friend who just said or did something reasonably stupid) to a scathing remark on the inane actions of a worthy idiot.


smooth move exlax definition by Urban Dictionary