Like a hot flash but instead it’s that brief period of time that you are extremely horny.
Wife to husband -“ want to turn on a movie for the kids and meet me in the bedroom?”
Husband to wife- “are you having a horn flash?”
When you aim your brasshole at the pressbox in a show
Band Director: OK, let's do a horn flash on this hit! We have to have shoulders in the form and brassholes to the box!