What means Auto-MDI/MDIX-Crossover?

MDI = Media Device Interface 
The RJ45 (copper) ports on the switch will automatically detect the cable type (straight-thru vs. cross-wired) and re-configure themselves accordingly. 

Content réference
Ethernet Military Switch RES-SCE-AC-8US
Ethernet Military Switch RES-SCE-8MG
Ethernet Military Switch RES-SCE-12MG
Ethernet Military Switch RESMLAC-8US-CAPS
Ethernet Military Switch RESMLAC-8MG-CAPS
Ethernet Military Switch RESMLAC-8MG-CAPS F35
Ethernet Military Switch RESMLAC-28MG
Ethernet Military Switch RJSMLAC-8UG-CAPS
Ethernet Military Switch RJSMLAC-8MG-CAPS
Ethernet Military Switch RJSML-8US1/8UG1
Ethernet Military Switch RJSML-MG7F3G