A chain of logic with ends so remote that to anybody else it seems to be completely unrelated. Like a wiki walk, but through your head, and there's no history.
Example of a non sequitard:
Alice: Hmm... I think Grassy Knoll Dew would be better thanMountain Dew.
<pause>
Bob: Would walruses fight for us in the zombie apocalypse if we gave them buckets?
Bob: Don't even try to figure out how I got there.
A secretary who is so incompetent at everything in her job description that she secretly throws people under the bus all day long because her only true skill is being a butt snorkeler.