Sentence:  But he could not write or speak English in a manner tolerable to any Englishman; and although he knew nearly all the words in the language, it was dictionary knowledge, and so different from an Englishman's apprehension of the same words that it was only a sort of <WSD>pseudo-English</WSD> that he knew, and not our living tongue. 
Meaning of the word marked with <WSD> tags:  (pejorative) English-language jargon or dialect that does not reflect the way most people speak.