"Star Wars" is a movie, says George Lucas, not a missile zapper, and anyone who says differently -- without permission -- had better watch out.

Lucas' company, which produced "Star Wars" and its immensely successful sequels, yesterday launched a legal attack against the television commercials that use the same name to refer to President Reagan's proposal for a space-based missile defense system.

The suit by Lucasfilm Ltd., filed in U.S. District Court here, accuses the political ad makers of trademark infringement, unfair trade practices and "disparagement" and seeks to have the ads changed or barred from the air.

Named as defendants are retired Army lieutenant general Daniel O. Graham, the leading advocate of the antimissile proposal, and a group Graham heads called the Coalition for the Strategic Defense Initiative (SDI).

Strategic Defense Initiative is the phrase the administration prefers to use for its plan. The tag "Star Wars" was given by its opponents, starting with Sen. Edward M. Kennedy (D-Mass.), just after Reagan proposed the weapons system two years ago.

In the propaganda war over SDI, however, Graham's group has fielded a 30-second television commercial that opens with a child's crayon drawing and a little girl saying she had "asked my daddy what this 'Star Wars' stuff is all about."

The ad is a counterattack to a television ad campaign launched last spring by the Union of Concerned Scientists, a disarmament group that has been a leading advocate of a "nuclear freeze."

The Union of Concerned Scientists resumed its anti-"Star Wars" ads last week. But according to the lawsuit, after a lawyer for Lucas threatened to sue to stop the ads, she was told on Friday that no further broadcasts of the commercials specifically referring to "Star Wars" were planned.

Graham's group refused to change its ad, and issued a statement attacking Lucas.

"We have tried unsuccessfully for more than two years now," Graham said, "to get the media and SDI critics . . . to stop using the term "Star Wars." As a matter of fact, our ad strives to change the nomenclature . . . to a more accurate description . . . 'the peace shield.'

"It seems strange that our group is called the culprit now," he continued. "The irony is that we couldn't agree more that the term 'Star Wars' should not be used to describe a defense that will defend populations against nuclear war."

Nancy Stockford, public information coordinator for the Union of Concerned Scientists, said her group regularly refers to the Reagan plan as "Star Wars," and may do so in future commercials, depending on how the court rules.

"We want people to feel it can't work, and that phrase definitely furthers our ends," Stockford said, "so people think it's just a fantasy anyway."

Authorized to use the trademark "Star Wars," according to the lawsuit, are various toy action figures, watches, paint sets, lunch boxes, socks, chewing gum, shampoo, bubble bath, candles, shoelaces, cookies, toothbrushes and video games -- but no space weapons systems.

Judge Gerhard A. Gesell has scheduled a hearing this morning on Lucasfilm's request for a temporary restraining order.