quieten /ˈkwaɪ.ə.tən/verb 2forms 3phrases 1 verb2 •(UK, Commonwealth) To make quiet.Take deep, deep breaths and quieten your mind while you contemplate what has been revealed within my latest journallings to you. — 2013 •(UK, Commonwealth) To become quiet.quieten down please, the speaker is going to start. formsquietened · quietening · quietens Phrases with quieten quieten downTo become quieter.