Carrie Underwood, 26, is a big, fat onion.

And if you don’t believe it, you can ask her.

“I’m a big, fat onion,” she said.

By that, she means she is a multi-layered person — not that she grows in the soil or induces crying jags.

Since winning “American Idol” in 2005, Underwood has become one of contemporary country’s most celebrated female vocalists, notching three consecutive top female vocalist prizes at the Country Music Association Awards — for which she’ll serve as co-host with Brad Paisley on Wednesday — and also at the Academy of Country Music Awards. On Tuesday, Nov. 3, Sony Music Nashville released the reigning ACM entertainer of the year’s third album, “Play On,” and after its first week it will likely top the country charts and the pop charts.

The first country female to score 10 No. 1 hits from her first two albums, Underwood is well known, and yet not known.

“I was talking with someone, and they were telling me about a conversation they had with someone I dated,” Underwood said. “The guy I dated said, ‘People don’t know her.’ I never really thought about that until this person told me about the conversation. I’ve had people say, ‘Hey, there’s really a personality in there. Don’t be afraid to be funny in front of people.’ I’m getting better with that, but when you open that book and let people in, there’s something scary about that. I guess I’m used to keeping people at a distance.”

At times, that distance is a must. During public appearances, Underwood is nothing if not on-point, and being on-point involves calculation and a professional calm and control. Most people don’t glad-hand at the office.

“When Carrie’s at work, she’s at work, but when you’re with her in a position where that’s not going on, she’s super cool,” said Chris Tompkins, who co-wrote Underwood’s smash “Before He Cheats” and who also co-wrote “Change” for “Play On.” “I’m glad I’m not an artist, with people coming up to you all the time, no matter where you are or what kind of mood you’re in.”

In conversation, Underwood is funny. Maybe not Bill Cosby funny, but the Cos doesn’t have her vocal range, either. She’s quick, though, and sharp. And she’s correct that those qualities don’t always come across in on-camera interviews. On “American Idol,” she learned quickly that being benign could be an asset.

“Oh, I never said anything on there,” she said. “Whenever judges would critique me, I’d keep my mouth shut. When I watch the show now and see someone talking back, I think, ‘There you go, you’re going home. I learned to keep the book shut when I was on Idol, because everything you do is so scrutinized. It kind of scares you into your shell.”

‘She’s a real human’

Underwood sees “Play On” as a concerted attempt to come out of that shell. She co-wrote more than 60 songs for consideration, and wound up recording seven of those. The styles and subjects vary as wildly as those things can vary in the country genre, as Underwood ricochets between anger and thankfulness in a way that seems fully suited to a single singer in her mid-20s.

Two songs use the word "jerk."