無駄口をたたく

むだぐちをたたく

to chatter pointlessly, to waste one's breath

無駄

むだ

futility, uselessness, pointlessness

無駄足

むだあし

visit for no reason, go on fool's errand

無駄花

むだばな

blossom which fails to produce fruit, non-fruit-bearing flower

無駄飯

むだめし

living idly

無駄金

むだがね

wasted money

無駄話

むだばなし

gossip, idle talk, chat

無駄骨

むだぼね

useless, waste of time and effort, pointless, vain efforts

無駄言

むだごと

chatter, idle talk

無口

むこう むくち

reticence, taciturnity

無駄食い

むだぐい

eating between meals, living idly

無駄遣い

むだづかい

wasting... on (e.g. money), squandering, waste, frittering away

無駄吠え

むだぼえ

barking over nothing (of a dog); barking at passers-by or visitors

無駄時間

むだじかん

dead time

無駄死に

むだじに むだしに

dying in vain

無口湖

むこうこ

endorheic basin

口無し

くちなし

something unspoken

無駄骨折り

むだぼねおり むだほねおり

laboring in vain or for no result, labouring in vain

無駄な医療

むだないりょう

medical futility