One who has a mania for music.

Off The Ground or OTG: When an attack is OTG it means that it hits off the ground. In MvC3's case it generally causes a groundbounce (although not all the time). For example, when Amaterasu is in her Glaive stance her charged Jumping H can hit OTG (hits knocked down opponent and causes a bounce) and can be followed up with another move or can be canceled into a Hyper. Other OTG moves are X-23's Ankle Slicer (?), and Wesker's (lower angled) Samurai Edge. Other moves such as Dante's Jam Session, pick up opponents.

off the grid. getting away from IM, email, SMS or other online activities to enjoy the real world for any specified amount of time.

Otg means “ out the gate” which in New Zealand is common slang for meaning something Or someone that is crazy.

Outside the gates. It's a term from the sci-fi show TerraNova and it means to go outside of the gates, literally. There is also a hidden meaning which is that to go OTG, it means to go beyond your limits or where you should not be.