Source : Free On-Line Dictionary of Computing

single static assignment
     
         (Also known as SSA form) A special form of code
        where each variable has only one single definition in the
        program code. "Static" comes from the fact that the definition
        site may be in a loop, thus dynamically executed several
        times.
     
        SSA form is used for program optimization or {static analysis}
        and {optimisation}.
     
        (2003-04-12)