when your "testicles" or "balls" are in the state of having a boner.
When you have had such an incredible boner aka the boner of your life, that the boner transfered to your ballsack.(note if you are a castroti "a guy gets his balls cut off this could be a problem! please contact your doctor for more information!)
OMG look at that girl i just had a ballner!
is it morning already! man i just had a morning ballner!
a guy: lets go to hooters!
some other guy: wouldnt it be embarrassing if we went ther and my ballner broke through my pants!