でかした (dekashita) is a somewhat old-fashioned expression that means “good job”, “great work, or “well done”. It contains a very light, non-serious tone, and is usually used when you praise someone younger than you.
When we hear this word, we picture a middle-aged man patting his subordinate’s shoulder at work. Therefore, this word is often used in anime or manga to illustrate a stereotypical old man or manly woman. However, some young people also use this word to sound casual and playful, as in the second example sentence below.
You: We’ve finally got a contract with company A!
Your Boss: Well done!
弟 (おとうと): 帰（かえ）りにアイス買（か）ってきてあげたよ
Your little brother: I bought you an ice cream on my way home.
You: Oh really? Great job!
Synonyms: よくやった (you did very well),
Synonyms in English: good job, great work, well done
Related words and phrases: でかしたぞ
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