Wiktionary
n. A sweetened, non-alcoholic, sparkling beverage with a wintergreen flavor, traditionally made from the oil of the sweet birch.
WordNet
n. carbonated drink containing an extract from bark of birch trees
Wikipedia
Birch beer in its most common form is a carbonated soft drink made from herbal extracts, usually from birch bark, although in the colonial era birch beer was made with herbal extracts of oak bark. It has a taste similar to root beer. There are dozens of brands of birch beer available.
Various types of birch beer made from birch sap are available as well, distinguished by color. The color depends on the species of birch tree from which the sap is extracted (though enhancements via artificial coloring are common presently). Popular colors include brown, red, blue and clear (often called white birch beer), though others are possible. This drink is most commonly found in the Northeastern United States, and Newfoundland in Canada. After the sap is collected, it is distilled to make birch oil. The oil is added to the carbonated drink to give it the distinctive flavor, reminiscent of teaberry. Black birch is the most common source of extract. In the dairy country of southeastern and central Pennsylvania, an ice cream soda made with vanilla ice cream and birch beer is called a Birch Beer Float, while chocolate ice cream and birch beer makes a Black Cow.
Alcoholic birch beer, in which the birch sap is fermented rather than reduced to an oil, has been known from at least the seventeenth century. The following recipe is from 1676:
Usage examples of "birch beer".
At first there was nothing but the underbrush growing from the spongy ground underfoot, and then you would see your first dumpoid: a rusty can that had once contained Prince Spaghetti Sauce, maybe, or an S 'OK sodabottle crawling with bugs attracted by the sweet-sticky remains of cream soda or birch beer.
She sensed the alcoholic character she had first tasted in the birch beer made by Talut, the Lion Camp's headman, but this was more like the fermented bilberry juice made by the Sharamudoi, except that that had been sweeter, as she recalled.
Solandia had shown her supply of fermented beverages, mostly birch beer, that she make the occasion festive.
There's a couple old bottles of birch beer, but I don't know if they're still good.
Passions he will admit to publicly include the Philadelphia Phillies, Michigan State University, New Jersey soul food (birch beer, pork roll, and Tastykakes), the Hammond B-3, and the Oregon coast.