Zebras on a field refers to the striped black and white uniforms worn by referees in sports such as soccer, basketball, and hockey. The term is derived from the pattern of the zebra's stripes, which resemble the stripes on the referee's uniform. The crossword solution for this term is REFS, which stands for referees. Referees are responsible for enforcing the rules of the game, making sure that all players abide by the rules, and ensuring that the game is played fairly.