This is the 9515th most frequent Russian word.
ушло
"Gone" or "left" (past tense, neuter form).
In this sentence, 'ушло' refers to the passing of time, indicating that it has 'gone away' quickly.
Время быстро ушло, мы не успели всё закончить.
Time flew by quickly, we didn't manage to finish everything.
Here, 'ушло' is used idiomatically to mean that the milk 'boiled over' or 'spilled out'.
Молоко ушло из кастрюли, когда я отвлёкся.
The milk boiled over from the pan when I got distracted.
In this context, 'ушел' (similar to 'ушло' but adjusted for the subject) means that the person physically 'departed' or 'left' the group.