We like Matt Yglesias' definition of a "chickenhawk" :

"One shouldn't advocate that your country go fight a war that you're not willing to fight in. If you told me, for example, that in order to invade Iraq successfully we were going to need to implement a draft and send fine young men such as Matthew Yglesias into combat, you can bet I'd start using my newfound free time to organize anti-war rallies. It's obviously a little hard to apply this line of thought to people outside a very narrow age-range, but since starting sometime in the early 1960s our country fought a very, very long war in Vietnam, we have a lot of historical examples of people's behavior we can look at. And we can see that Bush, Cheney, and many others in his administration failed it. They're "chickenhawks" because they supported that war, just not enough to actually go fight in it. That behavior, a willingness to sacrifice the lives of others for goals you recognize as not worth risking your own life over, is indicative of a reckless and immoral attitude toward war and peace in general, and that is a very legitimate issue to raise in this whole Iraq debate."