Is “Rider” a Scrabble word?
Yes
RIDER
Valid in at least one Scrabble dictionary
Valid in these dictionaries
SOWPODS / CSW
Scrabble UK & International
TWL / NWL
Scrabble North America
Large English Dictionary
General English word list
Meaning of Rider
/ˈɹaɪ.də(ɹ)/
noun
1.One who rides, often on a horse or a motorcycle.
2.A provision annexed to a bill under the consideration of a legislature, having little connection with the subject matter of the bill.
3.(by extension) Something extra or burdensome that is imposed.