A souterrain is an underground passage or chamber, typically constructed during the early medieval period, built from dry-stone walling and covered with large capstones. They are found in their hundreds across Ireland, usually associated with nearby settlement sites, and their purposes likely ranged from food storage and refuge to simple utility, though no single explanation covers every example.

The Nooan souterrain sits within a part of Clare that contains a broader scatter of early medieval remains, a reminder that the landscape was well settled and actively managed long before the arrival of Norman influence. These structures were generally built by hand, requiring considerable communal effort to excavate and line, and their survival over more than a millennium speaks to the solidity of the original construction as much as to the quietness of the ground above them. Beyond its identification and location, the specific details of this particular example, its dimensions, condition, any associated finds, remain thinly documented in publicly available sources at present.