Source : Free On-Line Dictionary of Computing

Tcode
     
        Intermediate language used by the Spineless Tagless G-machine
        (an abstract machine based on graph reduction) designed as a
        target for compilation of non-strict functional languages.
        "The Spineless tagless G- machine", S. Peyton Jones et al,
        Fourth Intl Conf Func Prog Langs and Comp Arch pp.184-201, ACM
        Sept 1989.