Definition (adjective): dressed or served covered with flaming liquor (such as brandy, rum, or cognac) — usually used postpositively, as in "crêpes suzette flambé"
Definition (verb): to douse with a liquor (such as brandy, rum, or cognac) and ignite
Flambé is the past participle of French flamber, meaning "to flame or singe," which is derived from the Old French noun flambe, meaning "flame." The é is followed by -ed or -ing in inflected forms of the English verb: "The crepes are flambéed with brandy." In the following example, the participle functions as an adjective.
Think, for example, of the way it feels when the marshmallow you have been meticulously roasting over a campfire accidentally catches. There’s a moment of pure thrill, an instant of terror, then you blow it out and eat it anyway. Some people even do this on purpose, chasing the fleeting moment when sugar and flame become one, the bittersweet flavor of char. A flambéed dessert takes this feeling and amplifies it in two ways: with the addition of alcohol, and with the move to the indoors. Setting your marshmallow on fire outside is one thing, but a flaming dessert served indoors takes the thrill to another level. It feels a bit more dangerous, almost illicit.
— Carina Finn, Eater, 15 Dec. 2020