This is the 7182nd most frequent Japanese word.
一昨年
The year before last.
Indicates an event taking place two years ago.
私は一昨年、日本に旅行しました。
I traveled to Japan the year before last.
Marks the beginning of an ongoing action starting two years ago.
一昨年から新しい趣味を始めました。
I started a new hobby since the year before last.
References the year two years prior relative to the current year.