The big books

So my darling son is sitting on the couch typing a paper into his computer for his class when he starts talking about sighting sources for his information.  I throw out a few things, one of them being Encyclopedia Brittanica, and he says what's that?  I said please tell me you know what that is, and he says oh!  yeah!  the big a** books!  Now, I am not fond of the language he used, but I couldn't help but laugh because of the description he used.  Cracked me up.