[Lewis Carroll, via the Michigan Terminal System]
1. A system failure. When a user's process bombed, the operator would get the message “Help, Help, Snark in MTS!”
2. More generally, any kind of unexplained or threatening event on a computer (especially if it might be a boojum). Often used to refer to an event or a log file entry that might indicate an attempted security violation.
3. UUCP name of snark.thyrsus.com, home site of the Jargon File versions from 2.*.* on (i.e., this lexicon).