say it: BEEST-lee
beastly is an adjective and adverb meaning "(informal) very unpleasant". It carries 3 recorded senses.
(informal) very unpleasant
“hellish weather”
“stop that god-awful racket”
colloquialism
resembling a beast; showing lack of human sensibility
“beastly desires”
“a bestial nature”
“brute force”
“a dull and brutish man”
“bestial treatment of prisoners”
in a beastly manner
“she behaved beastly toward her mother-in-law”
Forms marked · are formed by the regular rule rather than recorded in the source data. English keeps a few hundred irregulars and the rest follow the pattern, so the rule is right far more often than not — but it is a rule, and the mark says so.
Definitions, synonyms and semantic relations for beastly come from Princeton University’s WordNet. The pronunciation comes from the CMU Pronouncing Dictionary. Commonness is measured against a corpus of everyday English. Full sources and licences.