BY SOME ACCOUNTS, the Equal Employment Opportunity Commission has closed its doors to cases involving "comparable worth" -- the notion that jobs ought not to pay lower wages just because they tend to be held by women. But, in fact, the EEOC's decision is based on a definition of comparable worth that does not fit most cases in which sex-based wage discrimination is alleged. The decision should not be taken as a severe setback in the fight against sex discrimination in the marketplace.

As the General Accounting Office carefully lays it out in a new report, much of the raging debate over "comparable worth" turns out to be an argument over terms. One side defines comparable worth to mean one thing -- which it then attacks ferociously -- while the other side defends a totally different concept. The Reagan administration, speaking first through the Civil Rights Commission and now through the EEOC, has chosen to define comparable worth as a requirement that all jobs with the same value to the society be paid the same.

Against such a sweeping claim, it is easy to agree with EEOC Chairman Clarence Thomas that "Congress never authorized the government to take on wholesale restructuring of wages that were set by non-sex based decisions, by collective bargaining or by the marketplace." But the fact is that, as Mr. Thomas surely knows, such a claim is not being made -- at least not any longer -- by most proponents of comparable worth. They are using a more limited definition of comparable worth known as "pay equity."

By this less sweeping definition, an employer can still maintain different pay scales for jobs in which women predominate as long as the employer can show that such differences are justified by nondiscriminatory factors such as seniority, merit pay, skill shortages or collectively bargained agreements. But if the differences turn out to based in whole or in part on the employers' feeling that women don't need to support families, or on the fact that companies in the area have agreed not to bid up wages for secretaries, then the employer ought to be made to clean up his pay practices.

In fact, the EEOC says it agrees that cases should be pursued where there is evidence of actual sex discrimination in pay practices. And since most cases before the EEOC or state courts involve precisely such claims, last week's ruling may have little practical effect -- as long as there is no confusion about what EEOC actually decided.