Definition of once
(Entry 1 of 4)
1
: one time and no more
rode a horse only once went skydiving once
2
: at any one time : under any circumstances : ever
didn't once thank me
3
: at some indefinite time in the past : formerly
was once a booming mining town
4
: by one degree of relationship
first cousin once removed
once and for all
once in a while
1
: with finality : definitively
The team proved once and for all that they are the best.
2
: for the last time
I'm telling you once and for all that I'm not going.
: now and then
spent most of their time at home, but went out once in a while
once
noun
Definition of once (Entry 2 of 4)
: one single time : one time at least
Please be on time this once.
at once
once
adjective
Definition of once (Entry 3 of 4)
: that once was : former
a once successful actor
once
conjunction
Definition of once (Entry 4 of 4)
: at the moment when : as soon as
Once she spoke, I recognized her.
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Merriam-Webster unabridged
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The first known use of once was in the 12th century
See more words from the same century