regexp

regexp /reg'eksp/ n.  [UNIX] (alt. `regex' or `reg-ex')
   1. Common written and spoken abbreviation for `regular
   expression', one of the wildcard patterns used, e.g., by UNIX
   utilities such as `grep(1)', `sed(1)', and `awk(1)'.
   These use conventions similar to but more elaborate than those
   described under {glob}.  For purposes of this lexicon, it is
   sufficient to note that regexps also allow complemented character
   sets using `^'; thus, one can specify `any non-alphabetic
   character' with `[^A-Za-z]'.  2. Name of a well-known PD
   regexp-handling package in portable C, written by revered Usenetter
   Henry Spencer <henry@zoo.toronto.edu>.