Glossary of Terms:

omni on/mono mode

A MIDI device set to this mode will ignore MIDI channel assignments and respond to all incoming MIDI note data. It will also play only one note at a time.

Source: Yamaha: Sound Reinforcement Handbook

Related terms:   MIDI   omni   omni off/mono mode   omni off/poly mode   omni on/mono mode   omni on/poly mode