Definitions
American Heritage® Dictionary of the English Language, Fourth Edition
- adv. One time only: once a day.
- adv. At one time in the past; formerly.
- adv. At any time; ever: Once known, his face is never forgotten.
- adv. By one degree of relationship: my first cousin once removed.
- n. A single occurrence; one time: Once will have to do. You can go just this once.
- conj. As soon as; if ever; when: Once he goes, we can clean up.
- adj. Having been formerly; former: the once capital of the nation.
- idiom. at once All at one time; simultaneously: Everything happened at once. The view of the skyline is at once awesome, grand, and disappointing.
- idiom. at once Immediately; instantly: Leave the room at once.
Century Dictionary and Cyclopedia
- One time.
- One and the same time: usually with at: as, they all cried out at once. See phrases below.
- At one time in the past; formerly.
- At some future time; some time or other.
- At any time; in any contingency; on any occasion; under any circumstances; ever.
- Without delay; immediately: often merely expletive: as, John, come here once.
- Once for all.
- Immediately; forthwith; without delay.
- When at any time; whenever; as soon as.
- n. An obsolete form of ounce.
Wiktionary
GNU Webster's 1913
- n. The ounce.
- adv. For one time; by limitation to the number one; not twice nor any number of times more than one.
- adv. At some one period of time; -- used indefinitely.
- adv. At any one time; -- often nearly equivalent to ever, if ever, or whenever.
WordNet 3.0
- adv. as soon as
- adv. at a previous time
- adv. on one occasion
Etymologies
- Middle English ones, from on, one, from Old English ān; see oi-no- in Indo-European roots.
Examples
“Perhaps once, _once_, I might; but it is too late now.”
“_ _Yes, if it please you, once, and never but once_.”
“The Dutch have tired me out; and I intended to fight with them once, _only once_, and to drive them over the Vaal.”
With the Guards' Brigade from Bloemfontein to Koomati Poort and Back
“You will get this, father, when perhaps it is too late; but if you have any pity, any love left for your boy, come to me once more -- _once more_, father!”
“Not once -- not _once_, mind you -- had a single one of these great brains referred to the obvious.”
“Even now, once in a while, she -- but, thank heaven, not _once_ since meeting Lord Raygan; she was sure of that.”
“I had already encountered some of these creatures, once during my moonlight flight from the Leopard-man, and once during my pursuit by Moreau on the previous day.”
“Mrs. Brown says it was all most awful an 'she knows from her son's face as he thinks it was all because she stopped stirrin' sometimes durin 'the two hours an' she declares with tears as she never stopped stirrin 'once -- not _once_.”
“Oh, papa, dear papa, will you not let me -- will you not kiss me once, _just once_?”
“Never but once -- that uneffaceable _once_ -- had Agatha seen her husband look as he looked now.”
Lists
These user-created lists contain the word ‘once’.
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Words that are also movies
Unabashedly stolen from a comment made by courier12.
vertigo, serendipity, casablanca, psycho, jaws, fantasia, stagecoach, network, rocky, giant, platoon, unforgiven and 285 more...

sionnach Spanish for 'eleven'; it is also an acronym for one of the lotteries popular in Spain, run by the national organization for the blind. See, e.g.,
http://gaelstat.blogspot.com/2007/09/wanna-bet.html Jan 10, 2008