/bəg kəm-ˈpa-tə-bəl/
adj. Said of a design or revision that has been badly compromised by a requirement to be compatible with fossils or misfeatures 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."