Hangul syllable Keog

It marks a sharp choke, gag, or blocked breath.

Korean dictionaries describe two close readings: forcing out something lodged in the throat, or feeling your breath suddenly blocked. Choose the English wording from the scene; it is more bodily than a plain gasp of surprise.

컥 is built from the Hangul letters ㅋ, ㅓ, and ㄱ. Hangeul was created in 1443 and explained in 1446 as a writing system designed to make Korean easier to write. Earlier methods such as Idu, Gugyeol, and Hyangchal adapted Chinese characters to write Korean.

someone sent me 컥

Read it as a performed choke, not a fixed mood.

On its own, 컥! can act out a sudden choke or gag; in a line about breathing or something stuck in the throat, take that physical sense first. A playful exchange can make it theatrical, but the syllable alone does not tell you the sender's mood.

A 2021 study of Korean webtoons (digital comics) notes that sound words outside speech bubbles can carry atmosphere as well as dialogue. In that setting, 컥 can work like a visual sound effect. For a formal work message, use plain wording unless the joke is already clear.