scrimmage line vs line of scrimmage

scrimmage line and line of scrimmage both are nouns.

Word	Noun	Adjective	Verb	Adverb
scrimmage line	Yes	No	No	No
line of scrimmage	Yes	No	No	No

As nouns, scrimmage line and line of scrimmage are synonyms defined as:

scrimmage line and line of scrimmage: line parallel to the goal lines where football linesmen line up at the start of each play in American football

scrimmage line (noun)	line of scrimmage (noun)
line parallel to the goal lines where football linesmen line up at the start of each play in American football	line parallel to the goal lines where football linesmen line up at the start of each play in American football