beastly (adj.)

c. 1200, "brutish, sensual, debased;" late 14c., "in the manner of a beast," from beast + -ly (1). Weakened in British upper crust use to "awfully, exceedingly" by mid-19c. Beastly drunk is from 1794.

Beastly expresses that which is altogether unworthy of a man, especially that which is filthy and disgusting in conduct or manner of life. Bestial is applied chiefly to that which is carnal, sensual, lascivious: as, bestial vices or appetites. [Century Dictionary]

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Definitions of beastly from WordNet
beastly (adj.)
resembling a beast; showing lack of human sensibility;
beastly desires
Synonyms: bestial / brute / brutish / brutal
beastly (adj.)
(informal) very unpleasant;
Synonyms: hellish / god-awful
beastly (adv.)
in a beastly manner;
she behaved beastly toward her mother-in-law