Meryl Streep Explains Her Epic DNC Battle Cry: 'It Was a Moment In History'

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Meryl Streep made headlines with her elated scream just before addressing the crowd on night two of the Democratic National Convention on July 26. Now she's explaining the outburst to ET.

"That was like cheerleading at Bernards High School," Streep told ET, saying that the event gave her a feeling she hadn't had since her teenage years. "I was back there."

WATCH: Meryl Streep Screams for Joy Before Her DNC Speech

In the moment, which she called "terrifying," Streep spoke about the grit and grace needed to become the first female to accomplish something in any field, while giving Hillary Clinton her full endorsement.

"It was a moment in history. I really did feel the press of that," Streep told ET. "Think of it: 240 years we have been citizens, but only 100 years since we could vote and now the first female candidate for the presidency. I felt my grandmother's ghost accompanying me out there and my mother's and felt my daughter's pride. It was one for the whole team."

In her new film, Florence Foster Jenkins, Streep takes one for the team in a different way, as the Oscar winner -- a talented singer in real life -- has to sing badly for the role.

The biopic tells the true story of a New York heiress who did everything in her power to become an opera singer despite her terrible voice. But, no one around her had the heart to give her an honest critique of her talent or lack thereof.

WATCH: Lena Dunham and America Ferrera Team Up on Trump In DNC Speech: 'Love Trumps Hate'

Streep also admitted that she enjoyed every minute of her performance.

"It was so much fun," she said. "Toward the end we were actually trying to make it good and [director Stephen Frears] came in and said, 'You're singing too well.'"

Florence Foster Jenkins, also starring Hugh Grant and Simon Helberg, opens Aug. 12.