Defuse/Diffuse. "Defuse" is to stop a bomb from exploding. The old bombs were round things with a fuse coming out. You light the end, and it goes "Pssshhh... boom!" We are taking the fuse out. That's called de-fuse. We are taking it out so that the bomb can't explode any more.
"Diffuse" means that we spread out our attention - open out to others. This is what we're doing with the Compassion/Lovingkindness wish. You are thinking of yourself, another man your age, another women your age, one 10 years older, 10 years younger, and so on.
So, we are playing on the English language a little bit, but the essence is very important. We are going to stop the bomb we created inside ourselves, by spreading our attention and thoughts to other people who have similar problems.