As a Noun: 1. The night of the day before today. English = last night, yesterday night. 2. The night of the day before a particular day in the past. English = the previous night. As Modifier: 1. Used before or after a sign sentence to say the action in the sentence happened during the night of the day before. If you are already talking about something that happened on a day before today, 2. then you mean it happened during the night of the day before that day. English = last night; the previous night.