The blood-brain barrier.

(roofing) noncombustible board stock material of low thermal conductivity placed between two elements of a roof assembly.

(pathology, zoology) The inability of a disease to be transmitted from one species to a different one.

sound barrier

(rail transport) A manned barrier at which travel tickets are presented. Modern barriers are machines which can read tickets or where cards can be scanned before allowing passengers through.

a barrier to trade between countries in the form of high taxes or duties which may be imposed by a government.

plural of barrier rogue

(Australia, horse racing) A racehorse that is difficult to control when being put into the starting gates.

Synonym of sound barrier (sense 2).

(UK) A fence or barrier that divides the space occupied by a large crowd in order to prevent people from being crushed.