Dictionary.com/callow:

callow (KAL-oh) adjective

Lacking adult maturity or experience; immature: a callow young man.

Source: The American Heritage® Dictionary of the English Language, Fourth Edition
Copyright © 2000 by Houghton Mifflin Company.
Published by Houghton Mifflin Company. All rights reserved.

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adj : lacking experience of life; “a callow youth of seventeen” [syn: inexperienced, naive, unsophisticated]

Source: WordNet ® 2.0, © 2003 Princeton University

This word seems quite fun, and quite useful. I confess I have never heard it before, and that makes it perfect for our project!