bug-compatible
adj. Said of a design or revision that has been badly compromised by a requirement to be compatible with {fossil}s or {misfeature}s in other programs or (esp.) previous releases of itself. "MS-DOS 2.0 used \ as a path separator to be bug-compatible with some cretin's choice of / as an option character in 1.0."
bug-for-bug compatible
n. Same as {bug-compatible}, with the additional implication that much tedious effort went into ensuring that each (known) bug was replicated.
buglix
/buhg'liks/ n. Pejorative term referring to DEC's ULTRIX operating system in its earlier *severely* buggy versions. Still used to describe ULTRIX, but without venom. Compare {AIDX}, {HP-SUX}, {Nominal Semidestructor}, {Telerat}, {sun-stools}.