The Dead-Ball ERA was a period in Major League Baseball that lasted from 1900 to 1919. It was characterized by low-scoring games, a lack of home runs, and a reliance on the 'inside game' of bunts, stolen bases, and hit-and-run plays. The term 'Dead-Ball ERA' is derived from the fact that the baseballs used during this period were not as lively as those used in later eras. The three-letter solution for this crossword is 'ERA'.