The phrase "impenetrable barrier" refers to a situation or object that cannot be crossed, entered, or penetrated. It implies that there is no way to overcome or break through this barrier. Full definition
Different designs were tested on neurons grown in petri dishes alongside impenetrable barriers of proteoglycans. (sciencedaily.com)
On one hand you had acclaimed developer Omega Force and its popular Warriors franchise which, although divisive, enjoys a constant presence in the world of gaming, and on the other we had a less conservative Nintendo, breaking down the once impenetrable barrier built around its world - beating stable of classic series, with Zelda at the very forefront. (thesixthaxis.com)
On one hand you had acclaimed developer Omega Force and its popular Warriors franchise which, although divisive, enjoys a constant presence in the world of gaming, and on the other we had a less conservative Nintendo, breaking down the once impenetrable barrier built around its world - beating stable of classic series, with Zelda at the very forefront. (thesixthaxis.com)