No, the word barrier is not an adverb.

The word barrier is in fact a noun.

There are many types of barriers of communication for example; language barrier, physical barrier, emotional barrier, listening barrier, cultural barrier, gender barrier etc

It technically can be a barrier; a barrier between the water in the bucket and the ground.

Tuatara live in their natural refuges of Stephens Island and Brothers Islands in Cook Strait. Some have been transferred to the Coromandel, and Little Barrier.

But the Little Barrier population were threatened by kiore, the native rat, and a small breeding population was rescued and established on Hen island.

BARRIER - a blocking or physical interposition (e.g. "moisture barrier""Great Barrier Reef")