A Jaycee is a member of the Jaycees, a club with branches in many towns in the United States and in other countries too. The name is simply the letters J and C said as a word: they stand for Junior Chamber, short for Junior Chamber of Commerce — a younger people's business and community group. Members run local projects, raise money, and practise leading. You use it for this organisation, not for any young person in business. It sounds a little old-fashioned in everyday American talk now; you are more likely to meet it on a club sign, in a newspaper, or when someone is talking about civic work. Taiwan has the same international family of clubs, so a student may know the Chinese name better than this English nickname.