Source : Free On-Line Dictionary of Computing

nano-
     
        /nan'oh/ 1.  A {prefix} meaning 10^-9 or one billionth.
     
        Used loosely to mean "small", e.g. {nanotechnology}, or
        (rarely), following "nanosecond", to mean a short time,
        e.g. "I'll be with you in a nano".
     
        [{Jargon File}]
     
        (2002-03-02)