Definition from Wiktionary, the free dictionary
oncer (plural oncers)
- (informal, historical) A one-pound note.
1993, Will Self, My Idea of Fun:
- On whatever point Jane’s eyes rested, through whichever line her gaze ran, she saw cheques being signed, credit-card counterfoils being scrawled across, standing orders being arranged, and cash – wholesome dosh, ponies, monkies, oncers, coins of the realm – flowing around like mercury, like some element.
- (poetic) A person who does something once.
1944, W. H. Auden, The Sea and the Mirror: A Commentary on Shakespeare's The Tempest, Part 1. Prospero to Ariel:
- Could he but once see Nature as / In truth she is for ever, / What oncer would not fall in love?
- (informal) A single sexual encounter between two individuals, a one-night stand.
- (informal) A person with whom one shares a single sexual encounter, a one-night stand.