Never? Don't read the classics much (whether for pleasure or forced to in school)? To see it in a context outside this board, I would suggest chapter one of Pride and Predudice.
The only fool is one that fails to ask... and Cabron of course.
In this case, mean is a somewhat archaic usage meaning low in value or quality. Combine this with understanding, again somewhat archaic usage meaning intelligence. When combined in a sentence such as you are a man of mean understanding it can be translated into modern lingo as yur an idjit. </font>