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foul line

1 3.2

Lines that mark the side edges of a baseball field past first and third base

noun
/faʊl laɪn/

: línea de foul

He confidently stood at the foul line while waiting for the pitch to come.
foul line in the field
right-field foul line

Examples

Cassie walks on her hands along the third base foul line.

Fiction book (2001)
The ball landed just outside the foul line, resulting in a missed opportunity for a home run.
The player caught the ball right on the foul line, preventing a score from the opposing team.

Synonyms

sideline

vsfoul line

29 2.6

A line that marks the side of a playing field

is specific to baseball and runs past first and third bases

boundary line

vsfoul line

2 3.1

A line that shows the edge between two areas

is specific to baseball and marks field edges past first and third bases

Antonyms

fair territory

Jargon

5.2

Part of a baseball field between the first and third base lines where a hit ball is in play

Surface Forms

foul line singular

foul lines plural

Morphology

foul + line

The compound is compositionally built from 'foul' (relating to a rule-breaking or undesirable state) + 'line' (a boundary or mark), so a learner who knows both words can infer it denotes a boundary associated with fouls. However, the precise function and placement of the foul line are baseball-specific and the sense of 'foul' here is specialized, so the meaning is not fully predictable without sport knowledge.

Etymology

Foul line in baseball are the long lines from home plate past first and third base that show the field border. If the ball goes outside those foul lines it is 'outside the playing area', so the lines mark fair versus 'foul' balls.