riding vs horseback riding

riding and horseback riding both are nouns.

Word	Noun	Adjective	Verb	Adverb
riding	Yes	No	No	No
horseback riding	Yes	No	No	No

As nouns, riding and horseback riding are synonyms defined as:

As nouns, riding and horseback riding are synonyms defined as:

riding and horseback riding: the sport of sitting on the back of a horse while controlling its movements

Other synonyms of riding include equitation.

riding (noun)	horseback riding (noun)
travel by being carried on horseback	travel by being carried on horseback
the sport of sitting on the back of a horse while controlling its movements	the sport of sitting on the back of a horse while controlling its movements