In Irish English, deadly means brilliant or excellent. "That was deadly" = that was great. Not concerning, just regional vocabulary. If your kid uses it constantly, ask them where they first heard it, not to police their speech but to understand which online community they are in. Most slang of this kind moves through TikTok and group chats, so seeing it in your child's vocabulary just means they are plugged into normal teen internet culture.
deadly (Irish)
Irish: excellent, brilliant, top-tier.
Definitions
UK
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#1·Apr 24, 2026UK
Irish: excellent, brilliant, top-tier. "That's deadly" = "that's great." A cheerful Irish positive that sounds ominous to everyone else on first encounter, then becomes addictive once you use it.
Origin: Regional vernacular; long-established in its native community.
For parents
In Irish English, deadly means brilliant or excellent. "That was deadly" = that was great. Not concerning, just regional vocabulary. If your kid uses it constantly, ask them where they first heard it, not to police their speech but to understand which online community they are in. Most slang of this kind moves through TikTok and group chats, so seeing it in your child's vocabulary just means they are plugged into normal teen internet culture.
For ESL learners
Deadly in Irish English is an informal adjective meaning excellent or great. Use only in Irish English contexts. Formal equivalents: "excellent," "brilliant," "fantastic." Common non-native mistake: reading it as the standard sense (causing death). In Irish English the positive sense dominates in casual conversation. Pair freely as "deadly craic." Read or listen to the word in context several times before trying it yourself; the right register is harder to learn than the dictionary meaning.
Cluster: happy
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For specific readers
Why is this section here?
Slang is read by different audiences for very different reasons. The For parents view re-explains the term in plain, non-judgemental language so a caregiver can understand what their child means without needing the surrounding subculture. The For English learners view focuses on register (when it's safe to use), formal alternatives, and common mistakes — what a textbook won't teach you.
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UK
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UK and Irish slang — Cockney, Scouse, Geordie, Yorkshire, Glaswegian, Brummie, Welsh, West Country, plus Irish English. Centuries of regional dialects feeding into modern British and Irish street talk.
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Other words near "deadly (Irish)" (D)
deadfalldead fishdeadheaddead horsedeadhousedeaditordead mandead man walkingdead meatdead mendead moneydead on arrival
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