Is there a word or idiom to describe an attempt to win an argument through the introduction of a concept or word that is intellectually outside the grasp of the opponent?
For example, after a reasoned debate in a non-intellectual forum, where Side A has the upper-hand, Side B chimes in with:
"Well we just have different ontologies."
Side B's expectation being that Side A does not know what an ontology is, and therefore implying Side A should accept that there must be some substance to Side B's position based on his clearly superior knowledge.
Best Answer
You're talking about a type of argument and, more precisely, a type of fallacy. As described and as exampled in your question, the type could be one or more of several.
The most likely fallacy is the 'ad hominem':
(From "ad hominem" at About Education.)
This type, the 'ad hominem' most directly matches all the stipulations of your overall question.
However, the type of fallacy includes elements of the 'red herring', where the 'red herring' is the smokescreen offered by "ontology" which, as you describe it, may have no bearing on the argument.
(From The Nizkor Project, "Fallacy: Red Herring".)
To sum up, the word or phrase that best describes "an attempt to win an argument through the introduction of a concept or word that is intellectually outside the grasp of the opponent" is 'ad hominem argument', or 'ad hominem fallacy'. For the particular example you give of an 'ad hominem fallacy', the phrase 'red herring' also describes the argument.