Short definition
Wine served as individual glasses rather than full bottles, letting you try different wines throughout a meal.
Ordering by the glass gives you flexibility — different wines for each course, no commitment to a full bottle, freedom to experiment. The trade-off is price: a glass typically costs 25-40% of the bottle price, so four glasses costs more than buying the whole thing. Modern preservation systems like Coravin let restaurants offer expensive wines by the glass without oxidation. Ask what was opened recently — fresher is better.