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There is a Latin term or phrase (in wide use in English, esp academic discourse) that one uses in situations like the following:
one makes a statement or asks a question
one's interlocutor makes a response that is simply nonsensical: either per se, or which does not relate to the statement or question
The Latin (IIRC--could be Greek) term or phrase is adjectival, in that it describes (and implicitly denigrates) the response. I suspect it begins with 's' (but ICBW). I know I have used this in the past, but I simply cannot recall--please help!