diabolical

adjective

di·​a·​bol·​i·​cal ˌdī-ə-ˈbä-li-kəl 

variants or diabolic

ˌdī-ə-ˈbä-lik 

: of, relating to, or characteristic of the devil : extremely evil

a diabolical plot

diabolically

ˌdī-ə-ˈbä-li-k(ə-)lē 

adverb

diabolicalness

ˌdī-ə-ˈbä-li-kəl-nəs 

noun

Did you know?

Like the word devil, "diabolical" traces back to Latin diabolus, which itself descends from Greek diabolos, a word that literally means "slanderer." In English, "diabolical" has many nuances of meaning. It can describe the devil himself (as in "my diabolical visitor") or anything related to or characteristic of him in appearance, behavior, or thought; examples include "diabolical lore," "a diabolical grin," and "a diabolical plot." In British slang, "diabolical" can also mean "disgraceful" or "bad," as in "the food was diabolical."

Synonyms of diabolical

• demonic
• sinister
• malicious

Examples of diabolical in a Sentence

the police quickly mobilized to track down the diabolical criminals before they struck again

Recent Examples on the Web

On the first night of the diabolical competition show, contestants sat around another iconic table in The Traitors universe—the round table—while Cumming repeatedly circled, and then tapped on a few shoulders. —Alison McDermott, Architectural Digest, 19 Feb. 2026

As for why the vote in congressional races has tended to shift in Democrats’ favor, there’s a simple, non-diabolical explanation. —Mark Z. Barabak, Mercury News, 18 Feb. 2026

Dracula is the most well-trod of the three novels, its diabolical villain forever refusing to lie down and die. —Demetrios Matheou, HollywoodReporter, 18 Feb. 2026

As for why the vote in congressional races has tended to shift in Democrats’ favor, there’s a simple, non-diabolical explanation. —Los Angeles Times, 11 Feb. 2026

Word History

Etymology

diabolical from diabolic + -ical; diabolic going back to Middle English deabolik, borrowed from Middle French & Late Latin; Middle French dyabolique, borrowed from Late Latin diabolicus, borrowed from Late Greek diabolikós, going back to Greek, "slanderous," from diábolos "accuser, backbiter, slanderer" + -ikos -ic entry 1 — more at devil entry 1

First Known Use

15th century, in the meaning defined above

Rhymes for diabolical

• follicle
• symbolical

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Kids Definition

diabolical

adjective

di·​a·​bol·​i·​cal ˌdī-ə-ˈbäl-i-kəl 

variants or diabolic

-ˈbäl-ik 

: of, relating to, or characteristic of the devil : fiendish

diabolically

-i-k(ə-)lē 

adverb

diabolicalness

-i-kəl-nəs 

noun