At liberty, without obligations, as in Can you join us tonight?--Yes, I'm free as a bird, or He's free as a bird--he can travel wherever he chooses. [c. 1700]. Also see footloose and fancy-free.

The American Heritage® Dictionary of Idioms by Christine Ammer. Copyright © 1997 by The Christine Ammer 1992 Trust. Published by Houghton Mifflin Company. All rights reserved.