1. To become insane, mentally imbalanced, or crazed. Primarily heard in South Africa. I'm going moggy living in this shack all by myself!
2. To become extremely excited or enthusiastic (about something). Primarily heard in South Africa. I've never understood that pop star's popularity, but kids just go moggy over her music.
3. To act or do something wildly, excessively, and/or without restraint. Primarily heard in South Africa. We all went a bit moggy after our exams, hitting the bars every night for a week straight.