The Education Department, following legislation approved by Congress last summer, has proposed a rule prohibiting school districts from spending certain earmarked federal funds on any course that a district "determines is secular humanism."

However, the proposal, which defines several other concepts ranging from "magnet school" to "minority group," offers no guidance on what it means by "secular humanism."

The rule, and the law that spawned it, apparently represent the federal government's first official use of the term -- used pejoratively by some fundamentalist and conservative groups to describe everything from atheism to Darwinism -- since a footnote to a 1961 Supreme Court decision included "secular humanism" on a list of religions that "do not teach what would generally be considered a belief in the existence of God."

A group of liberal constitutional rights activists is trying to stir up opposition to the rule by bringing it to the attention of the press and public. But Democratic congressional aides familiar with the negotiations over the law argue that the very lack of a definition makes the prohibition harmless. One aide to its author, Senate Labor and Human Resources Committee Chairman Orrin G. Hatch (R-Utah), calls the debate "a tempest in a teapot."

In a comment to the Education Department, Anthony T. Podesta, executive director of People For the American Way, said, "Now, with a federal law that uses the term secular humanism without defining it, the Department of Education is making local school districts even more vulnerable to attack from those who have a history of using the charge of 'secular humanism' to oppose anything they don't like about public education."

In a pamphlet entitled "Is Humanism Molesting Your Child?," for example, a Fort Worth, Tex., parents' group described secular humanism as a belief in "equal distribution of America's wealth . . . control of the environment, control of energy and its limitation . . . the removal of American patriotism and the free enterprise system, disarmament and the creation of a one-world socialistic government."

According to Ed Darrell, a press spokesman for Hatch's committee, secular humanism "is almost a term of art. You get into value education and a bunch of touchy-feely stuff that came out in the '70s. Conservatives object because these things may get in the way of a Christian education . . . .

"That's a long way of saying there's no quick definition for it," he added.

Podesta's group, which was founded by television producer Norman Lear, urged the Education Department to define the term, saying it is unfair to place that burden on school districts. In comments on the regulation, he said, "Educators, scholars and theologians could share their research and views on the hoax of 'secular humanism.' "

But Paul Salmon, executive director of the American Association of School Administrators, said he was pleased "the department made the right judgment in allowing local school districts to define secular humanism."

Still, Salmon said he was "distressed that the federal government is trying to affect instructional programs . . . . They're trying to get a philosophical base for dealing with, oh God, everything from abortion to prayer . . . . People who criticize secular humanism are very fond of saying teachers are secular humanists."

The prohibition appears in a section of the Education for Economic Security Act that earmarked $75 million in grants over two years for "magnet schools" in districts undergoing desegregation efforts. Many of these districts lost millions of dollars in federal funds as a result of 1981 block-grant legislation.

That section of the law was drafted by Hatch, and, according to his aides, originally included a long list of prohibitions that were designed, in the words of one aide, "to focus the money on real, concrete academic subjects like biology or physics or real vocational subjects like auto repair, and to get away from the softer social engineering kinds of things."

However, according to Democratic and Republican congressional aides, most of the prohibitions were eliminated during a meeting between Hatch and Democratic Sens. Thomas F. Eagleton (Mo.) and Daniel Patrick Moynihan (N.Y.). For weeks before that June meeting, the pair of Democrats had blocked the legislation until they could win more aid for school districts such as St. Louis and Buffalo that were in the midst of massive, court-ordered desegregation efforts.

When the meeting was over, the only prohibition on curricula that remained in the bill was the one concerning "secular humanism."

In a statement issued this week, Moynihan said, "This was legislation essential to the desegregation of our schools. Preventing money for courses on secular humanism was a prime condition for Sen. Hatch's approval. Neither I nor anyone in that meeting room know of any school district that teaches secular humanism. I'm not sure anyone knows what secular humanism is. . . . Certainly no schools affected by this legislation " teach it.

"It should have had a definition. . . probably in the law," said a legal aide to Hatch. "But I don't necessarily think it was a mistake to prohibit it . . . . In part it's a symbolic thing. It has put the federal government on record saying that federal funds should not be spent on propagandizing an atheistic philosophy to our kids. If Mr. Lear doesn't like it, tough noogies."

Another Hatch aide, Ed Darrell, pointed out that the proposed rule lets school boards decide what a course using "secular humanism" might be. "School boards depend on sane, reasonable people running them," he said. "There is no definition you can build into federal law that can keep crazy people from misinterpreting things . . . . "

The absence of a working definition, he said, "was a glitch. But with a little luck it won't be a serious glitch."