Someone who reads catalogs of equipment -- high performance car parts, electronics or whatever -- and suddenly thinks he knows everything. These people are easy to spot -- they spend a great deal of money "improving" their cars, stereos or whatever. What they say sounds like hyperbolic ad copy and they won't let go of their beliefs, no matter how often someone proves them wrong.
Adam: Oh great, Ed's on a rant. He bought some gadget he found in a hot rod magazine for his car and claims it's doubled the power and his fuel economy. I looked at the thing and it's junk, just like all the other "performance parts" he bought in the last month.
Eve: That's Ed, alright. A real "Catalog Engineer."