Rebel vs Reb

Rebel and Reb both are nouns.

Word	Noun	Adjective	Verb	Adverb
Rebel	Yes	No	No	No
Reb	Yes	No	No	No

As nouns, Rebel and Reb are synonyms defined as:

Rebel and Reb: `Johnny' was applied as a nickname for Confederate soldiers by the Federal soldiers in the American Civil War; `greyback' derived from their grey Confederate uniforms

Other synonyms of Rebel include greyback, Johnny, Johnny Reb.

Rebel (noun)	Reb (noun)
`Johnny' was applied as a nickname for Confederate soldiers by the Federal soldiers in the American Civil War; `greyback' derived from their grey Confederate uniforms	`Johnny' was applied as a nickname for Confederate soldiers by the Federal soldiers in the American Civil War; `greyback' derived from their grey Confederate uniforms