Adjective hellish has 2 senses
- beastly, hellish, god-awful - very unpleasant; "hellish weather"; "stop that god-awful racket"
Antonym: pleasant (indirect, via unpleasant)
- demonic, diabolic, diabolical, fiendish, hellish, infernal, satanic, unholy - extremely evil or cruel; expressive of cruelty or befitting hell; "something demonic in him--something that could be cruel"; "fires lit up a diabolic scene"; "diabolical sorcerers under the influence of devils"; "a fiendish despot"; "hellish torture"; "infernal instruments of war"; "satanic cruelty"; "unholy grimaces"
Antonym: good (indirect, via evil)
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