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Literally, 冗談じゃない means "it is not a joke" but actually it seems that the
meaning of this is "something unthinkable even for a joke"( japanese
definition:冗談にもそんなことを言ったりするな。).

「道楽に働いているんだろうだって? 冗談じゃない.」

"I'm working for the fun of it? Nothing of the sort!"

「冗談じゃない、この暑い中に誰かと結婚するなんて！」

"Imagine marrying anybody in this heat!"
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2018-05-22T21:25:52.640
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2018-05-23T06:36:11.180
2018-05-23T06:36:11.180
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question
expressions
What is the logic of the expression "冗談じゃない"?
In the examples you provided, your interpretation is correct:

> but actually it seems that the meaning is "something unthinkable even for a
> joke"

In these cases, here are some additional expressions to capture the nuance

  * I'm not even joking.
  * Seriously.
  * Not even playing.

For this example:

> 「道楽に働いているんだろうだって? 冗談じゃない.」

I interpret this as "You think I'm working just for fun? Please!" (not as in
"pretty please")

For this example:

> 「冗談じゃない、この暑い中に誰かと結婚するなんて！」

I interpret this as "I'm not even halfway joking, who would seriously get
married to anyone in this heat!?"
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2018-05-22T23:44:56.157
58903
2018-05-22T23:44:56.157
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answer