= B =
1. In a regular expression or pattern
match, the text which was matched within grouping parentheses
2. The part of the pattern which refers back to the matched
text. 3. By extension, anything which refers back to something
which has been seen or discussed before. "When you said `she'
just now, who were you backreferencing?"
--The Jargon File version 4.3.1, ed. ESR, autonoded by rescdsk.