Wiktionary
n. A ladies formal glove that extends beyond the elbow.
Wikipedia
Ladies' evening gloves or opera gloves are a type of formal glove that reaches beyond the elbow.
Ladies' gloves for formal and semi-formal wear come in three lengths for women: wrist, elbow, and opera or full-length (over the elbow, usually reaching to the biceps but sometimes to the full length of the arm).
The most expensive full-length gloves are custom-made of kidskin. Many other types of leather, most usually soft varieties of cowhide, are used in making full-length gloves; patent leather and suede are especially popular as alternatives to kidskin, and are often more affordable than kidskin. Satin and stretch satin materials are extremely popular, and there are mass-produced varieties as well.