1. [common after 1997, esp. in the Linux community] An open-source software project is said to have forked or be forked when the project group fissions into two or more parts pursuing separate lines of development (or, less commonly, when a third party unconnected to the project group begins its own line of development). Forking is considered a Bad Thing — not merely because it implies a lot of wasted effort in the future, but because forks tend to be accompanied by a great deal of strife and acrimony between the successor groups over issues of legitimacy, succession, and design direction. There is serious social pressure against forking. As a result, major forks (such as the Gnu-Emacs/XEmacs split, the fissionings of the 386BSD group into three daughter projects, and the short-lived GCC/EGCS split) are rare enough that they are remembered individually in hacker folklore.
2. [Unix; uncommon; prob.: influenced by a mainstream expletive] Terminally slow, or dead. Originated when one system was slowed to a snail's pace by an inadvertent fork bomb.