There is "open carry" and "concealed carry", but I've never heard the usage you are asking about. I suppose that if one had a knife sheathed and attached to their belt, but was wearing a jacket that concealed the knife, that might qualify.

I know of people who were legally openly carrying a firearm and got convicted of carrying a concealed weapon because of a jacket. The laws vary by state, so such a thing is possible in some states.