This is the 775th most frequent Italian word.
compiuto
"Compiuto" means "completed" or "accomplished" in English.
The word 'compiuto' here means 'fulfilled' and indicates that the speaker has successfully completed a task or responsibility.
Ho compiuto il mio dovere come promesso.
I have fulfilled my duty as promised.
In this sentence, 'compiuto' is used as the past participle of the verb 'compiere' and means 'completed' to refer to the expected completion of an endeavor.
Il progetto sarà compiuto entro la fine dell'anno.
The project will be completed by the end of the year.
Here, 'compiuto' refers to 'turning' a specific age, hence 'compiuto' is used to describe the completion of eighteen years of age.