noun
half joking; half in jest
Used when something is said or done partly as a joke, implying the speaker is not entirely serious. Often appears in adverbial phrases like 冗談半分に.
彼は冗談半分に「辞める」と言った。
He said he would quit, half joking.
その提案は冗談半分だったが、意外にも採用された。
The suggestion was half in jest, but surprisingly it was adopted.
Compound of 冗談 (joke) and 半分 (half). The exact historical derivation is uncertain, but it follows a common pattern for yojijukugo expressing mixed states.