1. Medical phenomenon that occurs when a funny story ends in something sexual, illiciting a laugh and a boner.
2. Medical phenomenon that occurs when you are in a tickle fight with an attractive person.
1: Girl - "So, the bee flew down my blouse and I panicked, so I threw my shirt off, but I forgot I wasn't wearing a bra!"
Boy - "Haha... uh-oh... laughing boner"