A transpositional pun is a pun format with two aspects.
It involves transposing the words in a well-known phrase or saying to get a daffynition-like clever redefinition of a well-known word unrelated to the original phrase.
The redefinition is thus the first aspect, and the transposition the second aspect.
As a result, transpositional puns are considered among the most difficult to create, and commonly the most challenging to comprehend, particularly for non-native speakers of the language in which they're given (most commonly English).
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