DIABOLIC, DIABOLICAL adjective [Latin , the devil.] Devilish; pertaining to the devil; hence, extremely malicious; impious; atrocious; nefarious; outrageously wicked; partaking of any quality ascribed to the devil; as a DIABOLICAL temper; a DIABOLICAL scheme or action.
Source: Webster's 1828 American Dictionary ↗ · public-domain · returned verbatim, no AI