Wiktionary
a. 1 (context nautical English) not navigable; impossible to sail through 2 (context of a path, trail, or route English) that cannot be used for any reason.
WordNet
adj. impossible to sail through
Usage examples of "unnavigable".
She tried to still some of the anger, the pointless, unnavigable anger inside her.
Difficulties arose from the very outset, and not only had he to contend with the cannibals of Ugusu, but, in order to avoid many unnavigable cataracts, he had to convey his boats many miles by land.
Like the Vikings, whose shallow-drafted ships enabled them to sail up previously unnavigable European rivers and pillage villages - that rhymed - previously considered invulnerable to marine forces.
His home was a one-room tourist cabin at the end of a lane of crushed shells lined by dank mangroves bordered by an unnavigable lagoon.
The engineer had observed that it was increased by numerous affluents, but they were unnavigable, being simply little streams.
At the moment, it gilded everything with white, but it would soon turn the roads into an icy morass unnavigable by any sane man.
The stretch of water between the head of the Box Canon and the foot of the White Horse Rapids was unnavigable for steamboats and passengers were transshipped at that point, walking around the rapids from one steamboat to the other.
Difficulties arose from the very outset, and not only had he to contend with the cannibals of Ugusu, but, in order to avoid many unnavigable cataracts, he had to convey his boats many miles by land.
The engineer had observed that it was increased by numerous affluents, but they were unnavigable, being simply little streams.
Nobody can see me crossing the garden to the little stream, which is considered unnavigable.
And here th' access a gloomy grove defends, And there th' unnavigable lake extends, O'er whose unhappy waters, void of light, No bird presumes to steer his airy flight.