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REFERENCE

deadly

adj. · adv.
US //ˈdɛdɫi// UK //dˈɛdli// dead·ly
  1. 1 lethal (adj.)
    B2 Upper Intermediate

    able to cause death.

    capable of causing death; lethal or fatal in effect.

    Example

    The cobra has a deadly bite that can kill a person in hours.

    Example

    The researchers discovered that even a minute dose of the toxin proved deadly to most mammals within the ecosystem.
  2. 2 extremely accurate (adj.)
    B2 Upper Intermediate

    very accurate and effective, especially when aiming a weapon or a ball.

    highly accurate or effective; unerring in aim or execution.

    Example

    The striker has a deadly shot that rarely misses the goal.

    Example

    His reputation as a deadly marksman ensured that few dared to challenge him in the regional competition.
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  1. 3 very boring (adj.)
    C1 Advanced Informal

    extremely dull or uninteresting.

    extremely dull, tedious, or monotonous. Informal in register.

    Example

    The three-hour lecture on tax law was absolutely deadly.

    Example

    The meeting was so deadly that several board members were visibly struggling to remain awake during the financial presentation.
  2. 4 excellent (adj.)
    C2 Proficiency Informal Dialect

    very good or cool.

    excellent, impressive, or highly desirable. Primarily used in Irish and Newfoundland dialects.

    Example

    That new jacket you bought is deadly.

    Example

    The local band played a deadly set at the pub last night, drawing a massive crowd from the surrounding villages.

    Teacher's tip

    This sense is specific to certain regions like Ireland; learners should be aware it may not be understood in the US or UK.
  3. 5 extremely (adv.)
    B2 Upper Intermediate

    used to emphasize an adjective, meaning 'very' or 'completely'.

    used as an intensifier meaning extremely or utterly; often collocates with 'serious', 'dull', or 'quiet'.

    Example

    The room went deadly quiet when the principal walked in.

    Example

    The CEO was deadly serious when she announced that the company would be restructuring its entire European division.

    Usage

    Commonly used in the fixed phrase 'deadly serious'.
Origin

From Middle English dedly, dedlych, dedlich, from Old English dēadlīċ (adjective), from Proto-West Germanic dauþalīk, from Proto-Germanic dauþalīkaz (“deadly”, literally “deathly”). By surface analysis, dead + -ly. Cognate with Saterland Frisian dodelk (“deadly”), West Frisian deadlik (“deadly”), Dutch dodelijk (“deadly”), German tödlich (“deadly”), Swedish dödlig (“deadly, fatal, mortal”), Icelandic dauðlegur (“mortal”). The adverb is from Middle English dedliche, from Old English dēadlīċe (adverb), from the adjective.

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