In baseball, it's the area enclosed by the 3 bases & home plate
[DOC] [TLE] infield - definition and meaning - Wordnik [PAR] infield: Baseball The area of the field bounded by home plate and first, second, 
and ... n. the area of a baseball field that is enclosed by 3 bases and home plate... [DOC] [TLE] Standard Measurements in Sports - Infoplease [PAR] Here you can find the standard measurements used in baseball, basketball, 
bowling, boxing, ...