Medium Term Note - MTN
  
See: Medium Term. See: Long Bond.
A medium term note is like the porridge that's juuuust right. It's not a short-term note, which is usually due in a year or less, maybe 2 years in some books...then the long bond is a 30-year beast. And there exist longer bonds: Disney issued 100-year bonds early in the 21st century.
So a medium term note is one that comes due within, eh, 5, maybe 10 years...something like that.
Notes are usually the nomenclature for paper issued by the U.S. Government, i.e. very high quality, "certain" paper.