- a person holding very antiquated notions; reactionary.
- a person living in the backwoods; rustic.
Examples from the Web for mossback
There is the "old" farmer, there is the "new" farmer, and there is the "mossback."
The mossback cannot win, because he prefers a flintlock to a Mauser.
The mossback was wide awake now, and he muttered something about "another of those pesky porkies."Forest Neighbors|William Davenport Hulbert
Fig. 239 shows a mossback's house or cabin in the lake lands of Canada.Shelters, Shacks and Shanties|D.C. Beard
I also have sympathy for the mossback particularly because he is the man that needs attention.