A colloquial particle/adverb meaning “something like/like .../the likes of ...”. Often used dismissively or to give an example.
彼なんか気にしないでください。
Don't worry about someone like him.
テストなんかもう終わったことだ。
Things like the test are already over.
こんなことで悩むなんか馬鹿らしい。
It's ridiculous to worry about something like this.
コーヒーなんか飲みません。紅茶がいいです。
I won't drink coffee or the like. I prefer tea.