From Longman Dictionary of Contemporary English(just) for once(just) for onceRARELYused to say that something unusual happens, especially when you wish it would happen more often Be honest for once. Just for once, let me make my own decision. For once Colin was speechless. → once
Examples from the Corpus
(just) for once• Mrs Saulitis's cheerfulness was lost for once.• You can't fault Ayckbourn's production but, for once, his comic vessel has problems carrying such emotionally heavy cargo.• But for once his famous ability to blend laughter and pain is overcome by the weight of his subject.• In fact for once the human mussel-gatherers have come to the assistance of their natural competitors.• But Holmes, for once, was wrong.• Why not, for once, why not? 