open field

Short definition from Wiktionary

Noun

1. 1
   A large, unobstructed area of land with minimal cover, exposing troops to potential enemy fire with little opportunity to hide or take cover.
2. 2
   A situation with no obstacles or limitations; a clear opportunity to act freely or without significant competition.

Adjective

1. 1
   Of a farming system, in which each manor or village had two or three large fields divided into narrow strips of land individually cultivated by tenants or serfs.
2. 2
   Of a player, capable of obtaining yardage in a broken field.