LAS VEGAS (AP) -- It's as if Carrie Underwood's dress were a matter of national security. Gaining access to the superstar country singer's rehearsal Friday night required a few promises: no photos, no video and no describing the gown she'll be wearing Sunday for the Academy of Country Music Awards. But no one said anything about asking Underwood herself. "The dress that I'll be wearing during my performance is ... " she began to reply, then suddenly stopped herself, taking a beat to carefully each word. "It's big," she continued. "It's big. There's a lot — a lot of dress." In struggling to keep a straight face, Underwood seems perfectly aware this exercise in coyness was both ludicrous and important. "It's hard to describe," she said. "Kind of like water, maybe? Like red water? That sounds scary, doesn't it? Maybe like lava. It's like lava. Or icing. Red icing." Underwood loves to play the fashion game, especially at award shows. At last year's ACMAs, she had different costumes for the arrivals line, sitting in the audience and performing on stage. "Why not? There is a lot of great dresses out there," she said. "And I only have a certain number of nights to be able to wear them." Underwood and Taylor Swift, among the hottest and hardest-working acts in music today, have brought some serious girl power to what has been a club long ruled by boys. Underwood's nomination for entertainer of the year marks the first time a solo female has competed in the show's top category since 2000. In 44 years, only six female acts have won the title, the last being The Dixie Chicks in 2000. "I think the times they are a-changing," said Underwood, a six-time ACM winner who's also defending her two-year reign as top female vocalist. "I hope, my biggest hope, is that this is the first of many. And I'm not saying for me. I'm saying for women in entertainer of the year category. ... "These guys, they dress in T-shirts and jeans every night and they put on a show — a great show — and they work very hard. But we women, we've got the hair, we've got the makeup, we've got the heels, we've got the dresses. We get out there, and I might be willing to say we may have to work a wee bit harder than the boys." Speaking of boys, Underwood, has been photographed at recent Ottawa hockey games, is reportedly currently dating Senators center Mike Fisher. So is she a hockey fan? "I love sports in general," she replied. "And I love going to sporting events in general. ... I do like hockey, yeah. It's kind of been a recent development. I think I know all the rules. And, yeah, I do enjoy it."