MMCX is an type of antenna connector. Reverse MMCX means that the polarity has been swapped around so it won't work with normal MMCX connectors. This is sort of muckity muck is pretty common to get certification from the FCC (basically they try and make it as hard as possible for an Average Joe to put non-standard antennas onto commercial AccessPoints).
If you're lucky someone might post a picture of a ReverseMmcx connector here.
Check out a list of connectors, including a Reverse MMCX connector: http://www.hyperlinktech.com/web/connectors.html