noun
useless matter; futile act; waste of effort
Refers to something pointless, a wasted action, or idle thoughts. Often used in expressions like 無駄事を言う (to say something useless) or 無駄事をする (to do something futile).
そんな無駄事をしている暇はない。
There's no time to waste on such useless things.
彼はいつも無駄事ばかり言っている。
He's always saying pointless things.
無駄 is a more common and broader term for 'waste' or 'uselessness', used as a noun or na-adjective. 無駄事 specifically refers to a useless matter or act, emphasizing the thing or action itself.
Compound of 無駄 (むだ, 'useless') and 事 (こと, 'thing, matter'). The reading ごと is a rendaku form of こと.