be on the horn

1. To make use of or speak (to someone) on the telephone. Don't disturb me, kids, I'm on the horn to your father at the moment. After our dreadful meal that night, I was on the horn to the manager the very next morning. When I was growing up, it felt like my sisters were always on the horn to their boyfriends, which was so annoying.

2. dated To be lustful or sexually excited, especially of a man; to have an erection. Sarah became quite embarrassed when she noticed that her date was on the horn in the middle of the movie. Wow, I only caught a glimpse of my wife in that skimpy outfit and I'm already on the horn!