Bill Cosby accuser Janice Dickinson walks through the Montgomery County Courthouse after testifying on the fourth day of the comedian’’s sexual assault retrial. (Mark Makela/Getty Images)

Onetime supermodel Janice Dickinson regaled a courtroom audience on Thursday with a stream of anecdotes from her heyday, everything from partying at Studio 54 to having sex with actor Sylvester Stallone.

Laughter rippled through the usually whisper-quiet court crowd as Dickinson described a DNA test to determine whether Stallone was the father of her child. She’d had sex, she said, with another man in the same month as sleeping with the star of the “Rocky” films.

“He wasn’t the only contender,” she quipped.

The test showed Stallone wasn’t the father, Dickinson said, adding, “Thank God!”

But when Dickinson turned from testifying about background information related to her character to the topic of the day — her allegation that Bill Cosby drugged and raped her in 1982 — her jocular manner shifted. Glaring across the room at Cosby, Dickinson described the 80-year-old entertainer as a “monster.”

Cosby, who says he’s legally blind, stared toward the sound of her voice, his mouth fixed in a stony frown.

Dickinson’s appearance was one of the most highly anticipated moments of the comedian’s retrial on charges of drugging and sexually assaulting Andrea Constand, a former Temple University women’s basketball official. The ex-model is the best known of 60 women who have accused Cosby of sexual misdeeds. On the witness stand, Dickinson cut a striking figure, tall and slender with long brunette hair parted in the middle. She faced off in a rapid-fire battle of wits with Cosby’s flamboyant attorney, Thomas Mesereau, who is known for his near-shoulder-length, dazzlingly white hair.

Dickinson is one of five previous accusers called as witnesses to bolster the prosecution case in the intense and frequently dramatic first four days of Cosby’s retrial. Dickinson’s encounter with Cosby was set in motion, she testified, when the comedian called her while she was doing a modeling shoot on the island of Bali. Cosby had previously offered to mentor Dickinson, who was 27 at the time and eager to become an actress.

Cosby, who was 45 at the time, wanted to fly her to Lake Tahoe, where he was performing. But he asked whether she’d be willing to fly economy.

“I only fly first-class,” she remembered saying.

When she arrived, Dickinson said, she wasn’t feeling well. She told Cosby she was having menstrual cramps.

“Cosby said, ‘I have something for that,’ ” Dickinson testified. “And I was given a blue pill.”

Soon she felt “dizzy and woozy,” she said. Later, in Cosby’s room, she had the wherewithal to take a couple of snapshots of Cosby. The photos — a key piece of evidence to buttress her claims of spending time with Cosby — were displayed for the jury, which got to see the entertainer dressed in a multicolored checked robe and brown cap.

Eventually, she was so incapacitated that she “couldn’t get the words out I wanted to say,” Dickinson testified. “I was rendered motionless. I was thinking, ‘What the heck is he doing?’ ”

But the thoughts running through her head and the sensations of that night have stayed with her ever since: “America’s Dad on top of me,” Cosby’s cigar-breath and his body odor.

“He was gross,” she testified.

Before she passed out, she said, she felt pain between her legs, and when she awoke her buttocks ached. The next day, she said, she tried to confront Cosby at an estate owned by the owner of Harrah’s casino.

“That wasn’t cool,” she told him. But he didn’t respond, she said. Dickinson said that her career was thriving at that time and that she decided not to report the alleged incident because she had “conservative clients” — such as Vogue, Maybelline and Revlon — that “would not appreciate that I’d been raped.”

Dickinson’s account of that evening in Lake Tahoe came under withering attack by Mesereau, who hammered the former model with details from her memoir, which mentions slamming a door on Cosby, but does not include references to the alleged drugging and sexual assault. Dickinson did not appear intimidated, instead defiantly chiding him when he challenged her.

Mesereau succeeded in getting Dickinson to admit that parts of her memoir are not true. Dickinson said she consented to the publication because she was “broke” and needed to cover costs related to her two children. When Mesereau pressed her about untrue aspects of the book, she shot back, “So what?”

Dickinson said there was a big difference between a celebrity book and testifying under oath.

“You lied to get a paycheck,” Mesereau said.

“I don’t lie, sir,” Dickinson said, her voice rising. “Don’t call me a liar.”

Dickinson testified that her publisher and ghostwriter warned her that Cosby’s lawyers would block publication of the allegation, and she also feared that Cosby would use his power in the entertainment industry to damage her career.

Mesereau sought to undercut Dickinson’s character by saying she’d had affairs with married men, though that line of questioning was blocked by Steven T. O’Neill, the Montgomery County, Pa., judge overseeing the case. Mesereau also asserted that Dickinson had spread a false rumor about being pregnant with the child of Stallone.

Dickinson denied spreading rumors, saying she’d merely informed Stallone that she was pregnant and he might be the father.