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Criminal Minds Star AJ Cook Always Get Asked About The Definition Of Unsub

Even if you've only ever seen one episode of "Criminal Minds," it's likely you've heard the term "unsub," short for "unidentified subject." As David Rossi (Joe Mantegna) and his team try to piece together the lives of their perps, they are constantly throwing out unsub, so much so that it's a trademark of the show — even in the Paramount+ sequel series, "Criminal Minds: Evolution." 

A.J. Cook is part of the cast members back for "Criminal Minds: Evolution." The actress portrays Jennifer Jareau, an FBI agent we watch balance her demanding work life with her home life with fellow cop William LaMontagne, Jr. (Josh Stewart). Jareau wasn't always a profiler but became one in "Criminal Minds" Season 7. Cook's future on "Criminal Minds" was in doubt, though, in 2010 ahead of the sixth season of "Criminal Minds." After fan petitioning, she was given extra episodes to wrap up her character's story (via Deadline). In 2011, she did ink a deal to return to the series, arguably in large part thanks to "Criminal Minds" fans.

Early in the show's run, Cook revealed in an interview with fellow actor John Henson that the question she gets asked the most from supportive fans is the definition of unsub, a term she joked is peppered into "Criminal Minds" scripts on a fairly consistent basis.

AJ Cook thinks they may say unsub 50 times an episode on Criminal Minds

Speaking with John Henson about "Criminal Minds," A.J. Cook addressed the technical terms required in scripts that are necessary to the jobs being portrayed on screen, like unsub. Cook revealed that term alone inspired endless questions from fans.

"People ask me that all the time, 'What does unsub mean?' It means unidentified subject — the killer, basically. So that's a favorite one that we say at least 50 times per episode," she told Henson in their interview on Henson's "Watch This!," which ran from 2005 to 2007. Cook revealed in the same interview that the subject matter and dictionary's worth of words and phrases required for "Criminal Minds" to feel authentic enough appealed to her because she'd always been interested in psychology. 

"I've always been a big fan of psychology. That's always been so interesting to me," she said, revealing she would profile strangers in Los Angeles for fun. The unsub term is likely far more widely known today, in part thanks to its constant use on "Criminal Minds," a series that ended in 2020 but returned only two short years later in the form of "Criminal Minds: Evolution," where Rossi and his team continue chasing down unsubs.