National League

(baseball) Initialism of earned run average, a baseball statistic. / (electronics) Initialism of electrically reconfigurable array. / (military) Initialism of explosive reactive armor.

(baseball) The older of the two professional baseball leagues within Major League Baseball.

(geology) An instrument that monitors the slow surface displacement of an active geologic fault in the earth.

Turned over with the blade of a plough to create furrows (usually for planting crops). / (figuratively, rare) Well-trodden or well-researched, previously explored.