Ronda Rousey opens up as 2-to-1 betting favorite over Amanda Nunes

Amanda Nunes holds the UFC women's bantamweight champion belt. But her challenger at UFC 207 will enter Las Vegas' T-Mobile Arena as the favorite.

Former champion Ronda Rousey enters the Dec. 30 bout a -200 favorite, according to online betting website Bovada. Nunes, the champion, is a +160 underdog.

In layman's terms, that means you have to bet $200 on Rousey in order to win $100; while a $100 bet on Nunes lands you $160 if she wins.

Rousey is fighting for the first time since UFC 193 last November, when she lost to Holly Holm via knockout in Australia. Nunes is making her first title defense, having stopped Miesha Tate in the first round of their UFC 200 matchup in July.