A "chicken jibe" is the quick jibe you do when you see a wave coming your way that you aren't going to be able to:
sail over it before it breaks.....
sail over to the unbroken shoulder of the peak of the wave to get past it.....
sail up and over the whitewater that rolls in after the wave breaks.....
In other words, you "chicken out" and jibe quickly and sail toward shore to hopefully outrun the wave.
If you sail in the surf alot, you will learn to do chicken jibes when necessary.
As you ability to judge waves and your skills improve, you will do fewer chicken jibes, but at first, they will be your best defense against spending alot of time in the wash cycle and breaking alot of gear as a result of too much time in the wash cycle.
Hope this helps,