What do you call a response which does not address the question?

When some one is asked a question, sometimes if they are trying to avoid answering the question, they respond with something unrelated. What is the word for that response?

Eg. A: Why were you late? B: This bagel tastes good.

What I am looking for is the name of that response, not the action.

The response in that example could be called a non sequitur: 'a statement having little or no relevance to what preceded it'. This doesn't imply deliberate avoidance, however.

Evasion is a common word used to describe that activity. Other words are hedging, diversion...

an indirect answer; a prevaricating excuse; a trickery, cunning, or deception used to dodge a question, duty, etc; means of evading

To dodge a question is a useful expression:

• To evade (an obligation, for example) by cunning, trickery, or deceit: kept dodging the reporter's questions.

(from TFD)

The term for this is a non-answer. The practice of giving non-answers could be described as evasion, avoidance, dodging the question, etc. A non sequitur is a statement that doesn't follow logically from the statements/premises that came before it, but in my experience it's not used to describe non-answers.

In the legal world, such an answer would be called non-responsive and is a well-known type of objection that can be raised against a witness' testimony.

http://thelawdictionary.org/nonresponsive-answer/