An initiation in improv is the first statement or action that begins the scene. Strong initiations provide information and definition to what otherwise is an undefined scene with infinite possibilities. Strong initiations provoke a reaction from the other person, define characters, define setting, and/or show an important action. They can be verbal statements, physical actions, or a combination of both.
Add your own example of a strong initiation as a comment below!

Shannon
// Apr 11, 2010 at 8:38 pm
Six Flags was so much fun!
amanda 98.253.34.177 not found // Apr 8, 2010 at 7:50 pm
Hey Sally! we have to practice for science olympiad. State is in two days REMEMBER?
Jamie 192.168.32.18 not found // Apr 8, 2010 at 3:03 pm
Hey, there's a guy with a dead body and a shovel, he looks nice.
Noah M 192.168.32.18 not found // Apr 8, 2010 at 3:00 pm
Dude.... that guy seriously just set the christmas tree on fire because his brother hid his presents.....
"Hey!! You missed a spot!"