The Collaborative International Dictionary of English v.0.48:

Hyphenated American \Hyphenated American\
   An American who is referred to by a hyphenated term with the
   first word indicating an origin in a foreign country, and the
   second term being "American", as Irish-American,
   Italian-American, African-American, Asian-American.
   Used in reference to Americans of foreign birth or ancestry.
   When used of Americans of European ancestry, it is often used
   to refer to those who have a strong attachment to the
   ancestral country or its culture. It implies that the
   individual is imperfectly assimilated into American culture,
   and is sometimes used derogatively.
   [Webster 1913 Suppl.]