I found the following definitions and links on the net:

"As defined in Section 101 of the 1976 Copyright Act, this is a work prepared by an employee within the scope of his/her employment, or a work specially ordered or commissioned for use by another person in accordance with a written document as a contribution to a collective work, motion picture, audio/visual and other certain types of works, the nature of which is specifically defined in Section 101 of the Copyright Act. In the case of a work made for hire the employer is considered the author of the work under the Copyright Act (and unless the parties agree, otherwise owns all the rights in the work).

http://www.pandelirium.net/Studio/Terms.html

Copyright].
A work prepared by an employee within the scope of his or her employment or a commissioned work that the parties agree in writing to treat as a work made for hire. The real person, partnership, or corporation for which the work is prepared is considered to be both the author and the owner of copyright from the moment of creation of the work."

http://usinfo.state.gov/products/pubs/intelprp/glossary.htm

Hope this helps