Meaning of pollice verso*

pol•li•ce ver•so

Pronunciation: (pōl'li-ke" wer'sō Eng. pol'&schwa-sē vûr'sō), [key]
— Latin. Latin.
  1. with thumbs turned downward: the sign made by spectators calling for the death of a defeated gladiator in the ancient Roman circus.
Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease.