Synonyms for Know-it-all

(n) : someone who acts as if he/she knows everything and believes him/herself above others as a result, normally intended as a pejorative

°One who makes it appear as if they're an expert on a subject while there are also signals (subtly or blatantly noticeable) that they don't know very much on the subject or at least as much as they're acting like they do on the subject; pretending to knowledge on a subject matter -- normally intended as a pejorative.