でかした (でかした, dekashita) is a somewhat old-fashioned expression that means “good job”, “great work, or “well done”. It is also common to say “でかしたぞ (dekashita zo)”, where “ぞ (zo)” is a particle put at the end of a sentence to emphasize the statement. Since this is a casual expression, it is usually used when you praise your friends or someone younger than you.
When we hear this word, we picture an over 50-year-old man praising his subordinate at work. In particular, it is often used in anime to illustrate a stereotypical old man or masculine woman. Therefore, if you’re young, it is not the word you use to sound cool, but rather casual and playful.
You: I’ve just finished the work that you gave me last week!
Your Boss: でかした (great work, well done!)
Your little brother: I bought you an ice cream on my way home.
You: Oh really? でかした (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