In the episode, which was filmed prior to COVID-19 restrictions were put in place, the star shared the harrowing experience with Smith.
"When I lost my virginity when I was 18, I was more concerned with the shame that I was feeling at not having done it," she said.
"I was not abused or it wasn’t rape, but I didn’t say yes. I wasn’t gung ho about it. But I also didn’t say no. I just let it happen," she shared.
Willis, 32, kept the man's identity to herself but said he "didn't check-in" after their encounter.
"That’s where I feel like the man’s responsibility is. No means no, but what if you can’t say no?" she said.
The actress will also discuss body image during her interview. As she grew up in the spotlight, under the wing of her famous parents, Bruce Willis and Demi Moore, Rumer had to deal with a lot of criticism about her appearance.
"I would get myself into a situation, and at some point I had learned that if someone wants, values me sexually, or I feel like they desire me, then they are entitled to me," she said. "When I was like 14, because I was so shamed when all those blogs came out about how I looked, how my face looked, then my idea was that, 'Oh, well then, if I'm desired sexually, then I have value.'"
Rumer appeared on the show last year with her mother, Moore, and sister Tallulah Willis. In a candid discussion about substance abuse, Rumer opened up about her own addiction and her mother's.
When Moore relapsed in the early 2000s during her marriage to Ashton Kutcher, Rumer began abusing alcohol after she cut her mother off. She "started getting anxiety attacks about how bad I was going to feel the next day."
Both daughters didn't speak with Moore for three years.
Rumer, who once called 911 to save her mother's life, admitted to being angry at her desire to have another child.
"It was like, Oh, we’re not enough?'" she recalled.
"Part of the reason I moved out of the house was because after you had a miscarriage, I was like, 'Why are you so desperate to have another kid? I couldn’t stand the idea, but then I saw these pictures. I saw how big her stomach was and was like, 'Oh, my God. I’m so insensitive.'"
Moore had a miscarriage when she was six months pregnant with Kutcher's child. She opened up in her memoir, Inside Out, about the dark period of her life.
Moore shared that when she was 15, she was raped by a man who paid her mother $500.
The new episode of Red Table Talk airs on Tuesday, October 20, at 12 p.m ET on Facebook Live.