Hangul Syllable Ddweo

It is a syllable used to spell Korean words.

뚸 is a Hangul block built from a consonant and vowel. In Korean 2-set (Dubeolsik) mode, Shift+E enters ㄸ, and N then J enter ㅜ and ㅓ; the input method joins them as one syllable. The block supplies one syllable's sound inside a word, not a complete word meaning by itself.

Hangul was designed for Korean, whose spoken language differs from Chinese. Before it, Korean writing used Chinese characters, sometimes adapted through Idu, Gugyeol and Hyangchal to represent Korean words and grammar. The first record cited for the script is dated 1443; a 1446 book, Hunminjeongeum, explained the new writing system. Hangul appeared in Buddhist and Confucian books, practical publications, labels and personal letters while official documents remained mostly in Chinese characters; it received formal national status in 1894. Those milestones belong to Hangul as a script, not to 뚸 individually.

What does it mean when someone sends 뚸?

Read it as a fragment when no surrounding Korean word is present.

Inside a Korean word, the syllable contributes sound and the complete word gives the meaning. If it arrives alone, the block does not say whether the sender is showing an input result or quoting a longer word; ask for that context.