exec /eg-zek'/ or /eks'ek/ vt., n. 1. [Unix: from `execute'] Synonym for chain, derives from the exec(2) call. 2. [from `executive'] obs. The command interpreter for an OS (see shell); term esp. used around mainframes, and prob. derived from UNIVAC's archaic EXEC 2 and EXEC 8 operating systems. 3. At IBM and VM/CMS shops, the equivalent of a shell command file (among VM/CMS users). The mainstream `exec' as an abbreviation for (human) executive is not used. To a hacker, an `exec' is a always a program, never a person.