1.
trifling errand; small bit of business; minor task
A vague, self-deprecating way to refer to an errand or task one needs to attend to, without specifying the details. Often used as a polite excuse to avoid explaining what one is doing.
Usage
野暮用 is used when someone wants to mention they have something to do without going into detail. It is self-deprecating — the speaker downplays the importance of their task. It is a convenient way to politely decline an invitation or excuse oneself.
Etymology
From 野暮 (unsophisticated, uncool) + 用 (business, errand). The idea is that the errand is too mundane or unglamorous to be worth mentioning.
Similar words
用事 is a neutral term for errands or things to do. 野暮用 adds the nuance of something minor that the speaker prefers not to elaborate on.