The last shred of politeness is gone. The cool formality with which Jean Harris and her prosecutor fenced disappeared today.

And if there were ever any doubt whether Harris was concerned about her younger rival for the affections of the slain Dr. Herman Tarnower, they evaporated today as Harris, in a cool white rage, admitted that she had referred to her rival, in a letter to Tarnower, in "many unattractive ways."

"I called her 'dishonest,'" she told prosecutor George Bolen, referring to Lynne Tryforos, an assistant to Tarnower. "I called her an 'adulteress.'"

A look of distaste passed over her face, but there was no way out. "I think I referred to her as a 'whore,'" she said after a pause.

"You didn't use a word to refer to the doctor as well?" pressed Bolen, who had seen the letter and knew its contents perfectly well. "You didn't refer to her and the doctor, saying to the doctor she was 'his whore'?"

"I may have," Harris said. "I think I used the word 'psychotic whore'. . . ."

"Did you also use the word 'slut'?" the prosecutor asked.

The defendant turned for help to the judge, found none, and was forced to respond.

"It seemed synonymous," she said "A whore is a whore is a whore."

Her disdain was strong, as it had been throughout the day.

"So you were upset by the doctor's relationship with Mrs. Tryforos?" Bolen asked.

"It was being touched by something like that," said the former Madeira School headmistress, repeating a theme she had voiced often. "It was being touched by something that undercut my own integrity and Hy's integrity . . . and I couldn't walk away. . . ."

Harris, Tarnower's lover for 14 years, is charged with second-degree murder in the doctor's shooting last March in the bedroom of his Purchase, N.Y., home.

The prosecution, noting that Tarnower had been seeing Tryforos, insists that Harris shot the 69-year-old physician intentionally in a jealous rage. Harris claims she drove from Virginia to the doctor's home that night to commit suicide, and that her feelings about the other woman had nothing to do with her depression and despair.

Outrage toward Tarnower, and Tryforos, is a feeling Harris has denied throughout the trial, which began in October.

"I was annoyed," she told Bolen after he asked about her feelings when she threw Tryforos' clothing on the floor.

"I was annoyed," she repeated when she told of throwing Tryforos' curlers at a window.

But today, her sixth on the stand, Harris' rage emerged. She made a string of damaging admissions: that she had destroyed property belonging to Tryforos; that she had participated, with Tryforos, in an exchange of harassing late-night telephone calls; that she considered Tryforos a woman who "denigrated" Hy, a "second-rate" woman, "uneducated, not overly bright."

"Who he slept with was one thing," she said, "but this was a man who read Herodotus for fun. . . ."

There were other damaging admissions. Denying at first that she had destroyed any of Tryforos' possessions -- although she charged that Tryforos had destroyed $1,000 worth of her clothing -- Harris reversed herself when faced with the evidence.

"Didn't you, in a letter to the doctor, admit you destroyed property belonging to Mrs. Tryforos?" the prosecutor asked.

"I didn't destroy it. . . .Just some plaques she had made calling him 'Super-Doc' [that] I threw in the pond, and I told the doctor about it," she said. "And there were always valentines to the doctor in the car when I borrowed it, and I threw those away. . . ."

"Weren't those simply manifestations of her love?" Bolen asked.

"I think 'Super-Doc' buttons are pretty silly," responded Harris, who seems to direct what anger she feels at her rival, never at the doctor.

Under questioning from Bolen, she also admitted having participated for years in an exchange of harassing telephone calls with Tryforos. The admission came in the form of a denial that her lover had threatened to stop seeing her if she continued to harass her rival.

"Wasn't there a time in November 1977 when Dr. Tarnower told you that he would not see you anymore if you continued to harass Lynne Tryforos with phone calls -- that he would banish you from his affections if you continued to call Lynne?" Bolen asked.

". . . I never called to harass her. . . .I called her because she had called me for three years, three years of hell. . . .She called and left her number whenever Hy and I went on vacation. She called in the early-morning hours, and I finally called her up and told if she didn't stop harassing me I would call her, and I did it and Hy knew it. . . ."

Her admissions, invaluable to the prosecution, were possible for Bolen to obtain because of his possession of the "Scarsdale Letter," which Harris wrote to Tarnower the day he was shot and which the defense fought being made public.

Harris has called it a "whining" letter. It has yet to be put into evidence, but Bolen used it throughout the day, drawing information from it and using that as a wedge to prompt more information from Harris. Not knowing when, or if, it might be read seemed to unnerve Harris.

"It's a terrible letter," she said at one point. "It exposes Hy in a way I would hope he would never be exposed, and it would expose Lynne and myself too. . . .It's a very private letter. . . , but if you're going to use it, Mr. Bolen, don't play cat and mouse with it. I'd rather have it out on the table."

Bolen ignored that, but he referred to the letter repeatedly. He also presented the Harris-Tarnower affair in a very different light than the defense had.

According to the defense, Tarnower's affections for Harris were not fading. According to the prosecution, Tarnower had been trying to remove Harris from his life for months; had been trying to break off the relationship the last weekend they spent together, and had been trying to avoid having Harris attend a medical testimonial dinner to be held in his honor last spring.

"Isn't it a fact that in your conversation on March 6 he told you he invited Lynne Tryforos to that dinner and he did not want you to be there?" Bolen asked Harris. "Isn't it true that you called and begged Dan Comfort [a coordinator of the dinner] for an invitation to be there, and that the doctor told you at that time [that] he preferred Lynne Tryforos' company to yours?"

"I never begged," Harris said. "I never begged anyone for anything."

But she was forced to make a concession about the doctor that her attorneys had fought earlier in the trial. It had to do with love letters and a comment Harris made about how Tarnower, in the early years of their relationship, had sent her many more than the two love letters the prosecution had in its possession.

"And how many did he send you in 1980?" taunted the prosecutor, and, after she said none, "How many in '79, and '78?"

"None," said Harris, in a manner straightforward and composed. "None. His feelings were very different in the '70s than they had been. He was not in love with me, he was fond of me. I never got over being in love with him. I was still deeply in love with him."