D defs.my
Entry 1 sense Webster, 1913

Fiendish

/fēn'-dĭsh/ · Fiend·ish · IPA /ˈfiːndɪʃ/
01 a. Like a fiend; diabolically wicked or cruel; infernal; malignant; devilish; hellish.
  1. 1.
    Like a fiend; diabolically wicked or cruel; infernal; malignant; devilish; hellish.