Popular lore, or perhaps urban myth of sorts perpetuated into the modern-day, would suggest that the thumbs up gesture meant a gladiator would have been spared from death. According to a number of historians and researchers (e.g. see Pollice Verso on the site penelope.uchicago.edu), the opposite is true. Another misconception is that the brave and brawny gladiators were meat and potato kind of men. Apparently they were vegetarian.
In the continuing spirit of Vegetarian Awareness Month, here are some other links to our previous posts on Vegetarianism: