A person who plays baseball, either professionally or recreationally.
From 'baseball' (the sport, first appearing as a written word in the 1800s) plus '-er' (one who does), creating a straightforward occupational noun for athletes.
Baseball birthed its own vocabulary ecosystem—'baseballer' competes with 'ballplayer,' but only 'baseballer' includes the sport's name explicitly. American culture was so wrapped up in baseball that the sport essentially named itself into everyday speech!
Complete word intelligence in one call. Free tier — 50 lookups/day.