Is ’serious fun’ an Oxymoron or not?
The expression ’serious fun’ is indeed an oxymoron.
An oxymoron is a figure of speech that uses terms that have opposite meanings or that contradict. Oxymorons are generally used for rhetorical effect.
However, there are many popular oxymorons nowadays that are used in everyday language, just like “serious fun” that is not really meant as a paradox.
For the term serious fun, the word serious is simply meant to emphasize the degree of fun or enjoyment a person is having or plans to have.