10 letters · 12 points in Scrabble
adjective uncontrollably noisy
adjective marked by or causing boisterous merriment or convulsive laughter
originFrom uproar + -ious (a variant of -ous (“suffix forming adjectives from nouns, to denote possession or presence of a quality in any degree, commonly in abundance”)).
Etymology from Wiktionary, CC BY-SA 3.0