Chiefly British To an extreme degree; very.(adverb)
American Heritage(R) Dictionary of the English Language, Fifth Edition. Copyright (c) 2011 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.
Use "beastly" in a sentence
"Well, actually, the term beastly means beastly for a reason: because this is how beasts behave."
"To such a being the golden gates are closed; and the Easterners, whom he despised for what he termed their beastly lethargies, have taught me the real secret of the poppy."
"We cross lakes in beastly winds, whitecaps slopping over the sides of the canoes, then grind out in bony streambeds where the water dribbles through hundreds of yards of boulder and cobble."