The D.C. Court of Appeals has overturned a $375,000 jury verdict against Howard University and ordered a new trial in the case of Marie L. Best, a former professor who was fired by its School of Pharmacy.

In a 65-page opinion issued last week, a three-judge panel of the court declared that D.C. Superior Court Judge Carlisle E. Pratt was mistaken in ruling that Best automatically had tenure because the university gave her late notice that her contract would not be renewed. It said that issue should be determined by a jury, based on the university's general practice.

The judges said a jury also should decide Best's claim that she was the victim of sexual discrimination because of sexual harrassment, a charge on which Pratt ruled in Howard's favor.

The $375,000 verdict, handed down in January 1983, was the largest against Howard in a string of lawsuits filed by dissatisfied employes. In July 1982, a jury awarded Best $851,000 in the case, but Pratt ruled that this amount was too high and ordered a second trial, limited to the issue of damages.

John M. Clifford, Best's lawyer, said he would ask the entire Appeals Court to rehear the case and, if it refuses, go ahead with a third trial.

"Needless to say," Clifford remarked, "we're not overjoyed. But the only way we would drop this case is if they settle."

A spokesman for Howard said the university's legal counsel could not be reached for comment.