1. noun
a) <! colloq/slang? Short name for the disease mononucleosis
b) (UK, Australia) A bicycle or motorcycle trick where the front wheel is lifted off the ground while riding
2. adjective
abbreviation for monaural or monophonic; having only a single audio channel
Because many in the audience were very close to one of the speakers, the DJ decided to play the music in mono.
Wikipedia foundation.