Impossible to pass, cross, or overcome: impassable roads; impassable problems. (adjective)
American Heritage(R) Dictionary of the English Language, Fifth Edition. Copyright (c) 2011 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.
Use "impassable" in a sentence
"Apparently all the government has to do is invoke the term ‘State Secrets’ and the lawsuit hits in impassable brick wall."
"Well, on we go, -- driving across what you would call impassable streets, and lo! we are wedged up in a crowd, -- and such a crowd, -- a crowd of all nations."
"Dismissed in four paragraphs with no analysis of the so-called impassable barriers, while the Idaho/Montana route is extensive in the number of turnouts needing to be constructed, the number of small bridges needing crossed, and the extent of modifications needed to complete the route."