As a Noun: 1. The day after today. English = tomorrow. 2. The day after any given or particular day; the day after (another day); the next day; the following day. As Modifier: 1. Used at the beginning of a sentence or immediately next to a verb sign to mean the action being talked about will take place the day after today or the day after some other particular day. English = tomorrow, the next day, the following day. 2. Used at the beginning of a sentence or immediately next to a verb sign to mean the action being talked about took place one day after another specified day. English = the next day, the following day, the day after that.