UFC Fighter Ronda Rousey Gives New Meaning to the Term 'Knockout' Now, to the female fighter giving new meaning to the term knockout. She's attempting to keep her undefeated title in a grudge match tonight, as her popularity among fans soars. At the same time, as she's taking calls from hollywood. And reena ninan is on the story. Reporter: Good morning, guys. Ron ronda rounscy has several fights under her belt. And tonight, facing off against one she calls one of the hardest and prepared fighters. If you mix the power of "rocky," with the girl power of "tomb raider," you get close to rhonda rousey. At the young age of 26, rousey is the first woman to win an ultimate fighting championship. I need to keep thinking of things that people say are impossible because it's a little addicting proving people wrong. Reporter: And not just an knockout in the octagon. She showed off her physique in the body issue of 2012. And made "maxim" magazine's hot 100 list. It's her larger-than-life charm that makes her hard not to watch. Like in this "sportscenter" interview thursday. I'm extra violent. You have to let me know when to be cuddly. Reporter: Tonight, rousey is defending her title against her bitter rival. I think she has to hate someone in order to be able to fight them. Reporter: And the two have captivated fight fans and reality tv fans alike, with their trash-talking on "the ultimate fighter." I'm going to break this girl. Reporter: And her cage fighting dominance is undisputed. Now, rousey is looking to outgun some hollywood's toughest action heroes in "the expendables 3." And "the fast & furious 7." I think women should be in every career. Be able to be fighters. They should be able to do anything. Reporter: Don't let her busy schedule fool you. I call it the prefight chaos. I need it. Adding to the tension, she's never done a rematch before. That takes place tonight. And rousey's opponent says she wants to win by brutality. Scary women. I'm scared to watch. It reminds me that show "glow," remember that? You watch that? Let's -- your tv viewing habits --