[puhn] 
noun, verb, punned, pun⋅ning.| 1. | the humorous use of a word or phrase so as to emphasize or suggest its different meanings or applications, or the use of words that are alike or nearly alike in sound but different in meaning; a play on words. |
| 2. | the word or phrase used in this way. |
| 3. | to make puns. |
| pun (pŭn) n. A play on words, sometimes on different senses of the same word and sometimes on the similar sense or sound of different words. intr.v. punned, pun·ning, puns To make puns or a pun. [Origin unknown.] pun'ning·ly adv. |
A humorous substitution of words that are alike in sound but different in meaning (see double-entendre), as in this passage from Alice's Adventures in Wonderland, by Lewis Carroll:
“And how many hours a day did you do lessons?” said Alice, in a hurry to change the subject.
“Ten hours the first day,” said the Mock Turtle, “nine the next, and so on.”
“What a curious plan!” exclaimed Alice.
“That's the reason they're called lessons,” the Gryphon remarked: “because they lessen from day to day.”
