The phrase "mother of all bombs" is spoken for — applied recently to ordnance dropped on ISIS — but it is a fair description of the cinematic debacle Unforgettable.

The movie is bad, though in a certain kind of way. One day (very) soon, folks will be watching it on cable, downing pints of pinot, and groaning at the lurid, eye-popping tactlessness of Unforgettable, which staggers into the minefield of domestic violence like a drunk.

It has the subject matter of Big Little Lies and the sophistication of Showgirls. And you know it right away, as soon as you see Katherine Heigl, her blond hair pulled severely into a ponytail, shooting dagger looks at the beautiful woman (Rosario Dawson) who has just moved in with her ex (Geoff Stults) and daughter.

Heigl's expression is unmistakable and, loosely translated from the hundreds of original Lifetime movies, means I will destroy you.

It starts with petty battles over how the child is to be fed, clothed, and schooled, then escalates pronto into psychohysteria. Tessa (Heigl) goes online to snoop about her new rival's past and finds that Julia (Dawson) was abused by a boyfriend, and has of late lived anonymously in a state of abject fear.

This, in Tessa, inspires no sympathy. She instead senses opportunity, and uses her developing hacker skills to exploit the situation in the most heinously irresponsible way.

Sounds like Oliver Stone directing from a script by Joe Eszterhas, but the blame for this cannot be laid at the feet of the patriarchy. The movie is directed by longtime A-list producer Denise DeNovi and cowritten by Christina Hodson.

Did they have something else in mind — something with a different tone? Whitney Cummings has a supporting role as Julia's best friend, for instance, but her stand-up stage wit has not made it to the screen.

What we're left with is Heigl going full Mommie Dearest, striding through the movie in jodhpurs and leather boots, berating her daughter for poor horsemanship, or seated like a Disney villainess in front of her vanity, perhaps dreaming of poison apples. Cheryl Ladd has a small role as her mom, a blond Grendel who spawned this lunatic and instructed her in the ways of high-strung perfectionism.

The nonsense reaches a kind of peak (or valley) when Tessa and Julia, linked in some psychic cat-fighting plane of existence, engage in competitive sex.

But you know it won't be truly over until they enter the HGTV luxury home octagon (everyone in the movie is spectacularly rich), fireplace pokers drawn, no holds barred, no decorative object off limits. Let's hope there is Stainmaster carpeting in Tessa's Nancy Meyers fantasy home.

Through it all, I couldn't help but feel for Heigl, who left Hollywood for Utah, complaining of crummy, demeaning roles for woman. She gives her all to Unforgettable, perhaps to prove that she had a point.