The feeling after seeing that your bitchy ex-girlfriend has aged poorly, is obese or looks generally bad after some years.
Oh my God! have you seen Martha? she looks awful. What happened to her? I'm happy I dodged that bullet.
To get yourself out of a sticky situation. A close call.
"I almost ran over this squirrel in the street today, but I swerved and hit this sharp, jaggedy tree. So it's all good. I sure dodged that bullet, but missed and fell off the building."
If someone has dodged a bullet, they have successfully avoided a very serious problem.
Oh my lord! I just found out that my ex just had his second illegitimate baby. Dodged that bullet!