Final answer:
A 'pun' is a form of wordplay that uses the multiple meanings of words or similar-sounding words for humor or rhetorical effect, as in the exchange where 'very punny' responds to a pun with another pun.
Step-by-step explanation:
The word 'pun' refers to a play on words that exploits multiple meanings of a term, or words that sound alike but have different meanings, for a humorous or rhetorical effect. For instance, in a conversation, if someone delivers a pun and another person replies with "That's very punny!", this response is itself a pun that plays on the similarity between the words "punny" and "funny."
It indicates that the speaker has recognized the joke as a pun, while also layering another joke on top. This is different from a quadrain, which is a stanza of four lines in poetry, and is not necessarily related to wordplay.