Definition

1. Adjective:

   • Causing or capable of causing death: Describes something with the potential to be fatal or lethal.
   • Extremely effective or intense: Describes something so severe or potent that it resembles or could lead to a fatal outcome.
   • Extremely accurate or unerring: Describes precision or aim that is unfailing.
   • Complete or total: Used to emphasize an absolute, often negative, quality.

2. Adverb:

   • Extremely, intensely: Used as an intensifier to mean "to an extreme degree."
   • As if dead: In a manner resembling death.

Usage and Examples

• Adjective:

  • The boxer delivered a deadly blow to his opponent's jaw. (Capable of causing death or serious injury)
  • Careless driving is a deadly habit. (Likely to cause death)
  • The assassin had deadly accuracy with a rifle. (Extremely precise and effective)
  • There was a deadly silence in the room after the announcement. (Complete and oppressive)

• Adverb:

  • The lecture was deadly dull. (Extremely dull)
  • She is deadly serious about her career. (Extremely serious)
  • The patient's face was deadly pale. (As pale as a dead person)

Advanced Usage

• "The seven deadly sins": In Christian theology, the seven vices (pride, greed, wrath, envy, lust, gluttony, sloth) considered to be the origin of other sins and spiritual death.
• "Deadly earnest": Completely and utterly serious.
  • He was deadly earnest in his warning.
• "In deadly haste": With extreme urgency.
  • They fled the scene in deadly haste.

Variants and Related Words

• Deadliness (noun): The quality of being deadly.
  • The deadliness of the virus caused global concern.
• Dead (adjective): No longer alive. (Note: This is the root word, not a variant of "deadly").
• Deathly (adjective/adverb): Resembling or suggestive of death (e.g., ; ). Often similar to "deadly" but more commonly associated with the appearance or quality of death itself.

Synonyms

• Adjective: Lethal, fatal, mortal, virulent, venomous.
• Adverb: Extremely, exceedingly, terribly, dreadfully, deucedly.

Related Phrases and Idioms

• "Deadly enemy": A bitter, implacable foe.
  • The two nations were deadly enemies for decades.
• "Deadly weapon": An object designed or used with the intent to cause death or serious bodily harm.
• "Deadly dull/boring": (Informal) Extremely boring.
• "Deadly sin": See "The seven deadly sins" under Advanced Usage.

Adjective

1. (of a disease) having a rapid course and violent effect
2. exceedingly harmful
3. involving loss of divine grace or spiritual death
   • the seven deadly sins
4. extremely poisonous or injurious; producing venom
   • venomous snakes
   • a virulent insect bite
5. of an instrument of certain death
   • deadly poisons
   • lethal weapon
   • a lethal injection
6. causing or capable of causing death
   • a fatal accident
   • a deadly enemy
   • mortal combat
   • a mortal illness

Adverb

1. (used as intensives) extremely
   • she was madly in love
   • deadly dull
   • deadly earnest
   • deucedly clever
   • insanely jealous
2. as if dead