The phrase "at once defined" is correct and usable in written English.
It can be used to indicate that something is defined immediately or simultaneously in a particular context.
Example: "The concept of freedom is at once defined by its absence and its presence in society."
Alternatives: "immediately defined" or "simultaneously defined".
All are playing self-conscious roles — son, colleague, sibling and lover — that at once define and restrict them.
You walk along a great balcony and below you are shifting still images on the floor and walls video clips that recall dreams and notions of limitless skies that at once define the capsules of our hopes and wonderings through the last two millennia.
At the heart of its narrative Russian dolls and suggestive punning is a profound, ongoing exploration of identity: what does it mean, after all, if your cleverness, the trick that at once defines you and which you need to stay alive, reduces you to being "no one"?
The Soviet Union, with Russia at its core, once defined the refined art of ice dancing with a brief interregnum for the two-off English-accented transcendence of Jayne Torvill and Christopher Dean.
Places popular with the moneyed class like Daylesford are thriving, but the phone-hacking probe and political climate have chipped away at the gatherings that once defined the social scene.
In a different context, Russell Belk, a consumer-behavior expert and marketing professor at York University in Toronto, once defined the "perfect gift" as having specific characteristics, including the notion that it is something the recipient is "delighted" to receive.
Under increasing economic and psychological pressure (prescriptions for antidepressants increased by 22percentt in New York at the end of September), arguments once defined by angry words can escalate when guns are available.
The chef Alex Stupak, who has always served tacos at Empellón Taqueria, recently put them on the menu at Empellón Cocina, which he had once defined as the restaurant where he would not serve them.
Once defined, every limit must be reached.
In sepia-toned fantasy portraits, Joy Goldkind's costumed characters play roles that are at once strictly defined and elusive.
