Film critics know it's January when they spend a good part of the morning puzzling out the proper nominal conversion of the word "asinine" ("asininity"? "asininishness"?). This is because so many of the movies they're seeing during this dreary month -- when studios routinely dump subpar cinematic products on the marketplace -- earn the distinction. And there are only so many graceful ways to describe material best referred to in euphemisms for barnyard efflux.

To wit: "National Security" and "A Guy Thing," two putative comedies that might entice teenagers into multiplexes for a boffo opening weekend but with any justice will be summarily sent packing by the resulting word-of-mouth (taking "Just Married" with them). Hey, a girl can dream.

She can also offer fair warning: "National Security," a by-the-numbers sop to adolescent testosterone overload, stars Martin Lawrence and Steve Zahn as two security guards who must team up to foil a plot by someone to do something with another thing that's very bad. To be honest, the din from the incessant car chases, shootouts and Lawrence's irritating signature line, "What the problem is?," drowned out the plot's finer points. Lawrence's appeal is still incomprehensible -- to call him a poor man's Richard Pryor libels not just Pryor but also the 33 million Americans currently living under the poverty line. Zahn, as a Los Angeles police officer who loses his job, girlfriend and last shred of self-respect thanks to Lawrence's character, is very funny and capable of serious acting. Sadly, neither gift serves him well in the role of a mere straight man. To be fair, there is one genuinely comic sequence in "National Security." It comes when Zahn's character is making an arrest and tries to swat away a bumblebee with his billy club. A bystander captures his flailing and kicking on videotape, and what looks like a case of Rodney King redux becomes a citywide scandal.

"National Security" continually plays with assumptions about race, but without much commitment or ingenuity. That's too bad: With a smarter star, the movie might have been a cheeky satire like last year's "Undercover Brother." In any event, Lawrence is either unwilling or unable to challenge himself or his audience. And that's what the problem is.

With its mania for anything that can crash, burn or go boom, "National Security" could easily have been called "A Guy Thing." Instead, that title has been appropriated by a wan romantic comedy starring Jason Lee. This promising young actor plays a man who meets the girl of his dreams (the suitably dreamy Julia Stiles) just a few days before his wedding to Miss Right (Selma Blair, who seems destined to be cast as the persnickety girlfriend).

The three leads in "A Guy Thing" are usually terrific, as are supporting players Shawn Hatosy, James Brolin and Diana Scarwid. All have unfortunately come under the sway of the same guys who perpetrated "Meet the Parents" (writer Greg Glienna) and "Snow Day" (director Chris Koch) on the unsuspecting public, proving that venality will outmuscle talent every time. Trying desperately to lower the bar for scatological gags, rank sexual humor and cheap physical shots, "A Guy Thing" features an uncharacteristically lackluster performance from Stiles, who seems constantly to be asking herself whether her time wouldn't be better spent studying for a college midterm or something. It would have been. If there is a God -- and if He spends a fraction of His time worrying about the fates of overpaid young actors -- the lead players have already moved on to better things.

Fortunately, audiences don't need divine intervention to save them from "A Guy Thing" and "National Security." They can avoid them and pray that January will end miraculously early this year.

National Security (89 minutes, at area theaters) is rated PG-13 for violence, language and some sensuality.

A Guy Thing (101 minutes, at area theaters) is rated PG-13 for language, crude humor, some sexual content and drug references.

Julia Stiles and Jason Lee star in "A Guy Thing," and Martin Lawrence headlines "National Security."Martin Lawrence, left, brings nothing but his typical irritating performance to "National Security," while the more capable Selma Blair and Jason Lee are wasted in the low-rent "A Guy Thing."