In physics, what is the definition and an example of diffraction?
Thank you.

I would recommend googling before you ask, but in case you did, here it is. "It is described as the apparent bending of waves around small obstacles and the spreading out of waves past small openings."
Say you have an opening and a light source behind it. As the light passes through the slit, it seems to bend around it.

And
http://www.newgeology.us/WaveDiffraction.gif
If you need more depth, Google it. Otherwise I would just be googling it for you

http://upload.wikimedia.org/wikipedia/commons/3/3c/Wave_Diffraction_4Lambda_Slit.png

The first link didn't make it, sorry