first blood

/F ER1 S T B L AH0 D/
noun
  1. 1

    The winning situation in a duel in which the first one to draw blood from the other wins.

  2. 2

    The first damage or reverse inflicted on an opponent in a conflict.

  3. 3

    The first score in a competition.

Source: https://en.wiktionary.org/wiki/first%20blood