An individual who purchases large quantities of firearms, camouflage, knives, body armor etc. that they have absolutely no practical use for.
The typical catalog commando has either very limited or no military experience. They just dress that way because they believe it makes them look tough, cool and like they know what they are doing.
Another quality of the catalog commando is that they rarely (if ever) smile when they're picture is being taken. They will stand there attempting to look intimidating with an unconvincing thousand yard stare.
Firing range safety officer - "Why are you wearing camouflage and body armor to an indoor pistol range? Wait a minute, are you that catalog commando Nutnfancy?
Nutnfancy - "Yes."
Firing range safety officer - "My god, you're even more pathetic in the flesh. NOW GET THE FUCK OUTTA MY RANGE DOUCHER!!!!!"