"Poltergeist," a fitfully witty and reliably spine-tingling horror melodrama about a pleasant suburban family threatened by increasingly unpleasant specters that invade their home, abduct the youngest child and ultimately dismantle the joint, derives its title from a German term meaning "noisy ghost." Opening today at area theaters, the movie appears a cinch Gothic sensation at the box office.

The movie looks and feels decidedly patchy, as if it had been assembled by different hands frequently working at cross-purposes. According to widespread rumor, the director of record, Tobe Hooper, stepped aside for co-producer Steven Spielberg. The premise and the technique of systematically juxtaposing comic and scary touches may be easily recognized as Spielberg trademarks. The suburban settings in "Poltergeist" and the upcoming "E.T.," an acknowledged Spielberg credit, are obviously similar and identifiable as his characteristic social terrain.

But while it works you over effectively, "Poltergeist" betrays a good deal of rather dubious, uncoordinated manipulation. On one hand Spielberg is determined to unleash a hellish host from the spirit world, but on the other he doesn't want any of the characters to be seriously harmed by contact with these demons. Just shaken up. In a similar respect, highly abstract concepts of the supernatural tend to get overwhelmed by crudely graphic forms of spookiness. Eventually, the spooks seem all too visible and literal. There are too many of them rattling, banging, lurching, slithering and generally wallowing around for the good of a story that suggested interesting possibilities at the outset.

A crucial mistake is the lack of any tension in the victimized family. The Freelings are an attractive but innocuous group, consisting of mom (Jobeth Williams), dad (Craig T. Nelson), teen-ager (Dominique Dunne), a boy of 10 or so (Oliver Robins, presumably playing Spielberg's apprehensive alter ego) and the little girl, whose amazing disappearance triggers an escalating series of outrages.

As a rule, stories of this sort tend to profit from the suggestion that malignant spirits have been given an opportunity by some hidden source of conflict or unconscious psychological turmoil within the family group. In this case they appear to project themselves into the present without the cooperation of a living soul. It's a strictly external attack on a happy home, and though we learn that the spooks have very specific grievances, these are connected with the locale rather than the people who happen to live there.

Carol Ann's disappearance is an ingenious variation on the capture of little Barry by the extraterrestrials in "Close Encounters." In this case the child is attracted to spectral playmates who talk to her through the snowy flickers of a television set that the drowsy Mr. Freeling neglects to turn off. If "Psycho" gave people a phobia about showers, "Poltergeist" is likely to remind spectators of the importance of turning that thing off before you fall asleep, lest a disembodied spirit slip through the cathode static and suck a member of the family into electronic limbo.

There are signs of something supernatural in the house before Carol Ann is abducted, but the early manifestations are whimsical--the furniture gets rearranged, for example, or you can be whisked across the kitchen floor by some invisible force if you sit on a particular spot. Certain episodes reflect a comic authenticity that must come straight out of Spielberg's childhood, particularly a sequence in which Mr. Freeling tries to reassure his kids about the sound of lightning.

After the kidnaping introduces a clear note of urgency into the plot, it would probably be preferable to concentrate on the reactions of a particular member of the household. Under the circumstances, Mrs. Freeling seems the appropriate character, and while the plot eventually obliges her to seek out Carol Ann in realms of the supernatural, the script lacks an adequate appreciation of what this fantastic quest requires in terms of nerve and character. If the mother-daughter relationship were thought out more logically, the effort demanded of Mrs. Freeling might generate more heroic impact.

The dramatic focus shifts from one adult character to another--now it's the mother, then the father, then Beatrice Straight as the leader of a team of parapsychologists, and finally the diminutive Zelda Rubinstein as an intrepid psychic, who actually can unlock doors admitting passage to the supernatural. The diffusion seems to underline the gratuitous, miscellaneous nature of the ghostly assaults.

Parents should probably be alerted to the fact that the PG rating is a borderline call. Originally, the film was rated R, but the judgment was eased upon appeal. Although I've certainly seen more ghoulish and terrifying spectacles erupt from the screen, "Poltergeist" seems grisly enough to be approached with caution and kept offbounds for younger children. Even if no harm comes to the characters in the long run, there's something peculiarly insidious and threatening about the destruction of their home.