Dictionary.net

Old software (especially applications) which one is obliged toremain compatible with, or to maintain. DP types call this"legacy code", a term hackers consider smarmy and excessivelyreverent. The term implies that the software in question is aholdover from card-punch days. Used especially when referringto old scientific and number crunching software, much ofwhich was written in Fortran and very poorly documented but isbelieved to be too expensive to replace. See fossil;compare crawling horror.