(of a path, trail, or route) That cannot be used for any reason.
The trail was unnavigable since the flood washed it away.
Unnavigable Sentence Examples
All are swift and unnavigable, save perhaps for a.
It is lowest in November, and rocks, shallows, and the remains of old dams then render it almost unnavigable.
Pascagoula and Point aux Chenes bays; separated from it by the shallow and practically unnavigable Mississippi Sound is a chain of low, long and narrow sand islands, the largest of which are Petit Bois, Horn, Ship and Cat.