Cascadian adjective 1noun 1forms 3 adjective1 •Of, pertaining to, or characteristic of the Cascadia region of North America.All the evidence, starting with the layer of sand, points to a Cascadian earthquake during the night of January 26, potentially as big as the Sumatran one of 2004. — 2009 noun1 •A resident of the Cascadia bioregion of North America. formsCascadians · more Cascadian · most Cascadian