Wiktionary
n. A style of colourful silk kimono distinguishable by its long sleeves, associated with the formal celebration of Wikipedia:Seijin shiki by a young woman reaching the age of 20.
Wikipedia
A is a style of kimono distinguishable by its long sleeves, which range in length from 85 centimeters for a kofurisode (小振袖) to 114 centimeters for an ōfurisode (大振袖). The sleeves are attached to the body of the kimono only for a short distance; the inner edge is open for the rest of its length, allowing the lining to show on the inner edge (or both, if the sleeve is left open on the outer edge as well).
Furisode are the most formal style of kimono worn by young unmarried women in Japan.
The furisode is made of very fine, brightly colored silk, and is commonly rented or bought by parents for their daughters to wear when celebrating Coming of Age Day the year they turn 20. By wearing a furisode, a young woman signifies that she is both single and a legal adult, and thus available for marriage. In this sense, a furisode might be likened to the formal gowns worn by debutantes in the West.
The furisode is generally worn for formal social functions such as the tea ceremony or wedding ceremonies of relatives. Since furisodes can be quite expensive, many women rent them as needed rather than purchasing them.