week. 1. a period of seven successive days, usu. understood as beginning with Sunday and ending with Saturday. 2. a period of seven successive days that begins with or includes an indicated day: the week of June 3.3. (often cap.eek from Monday-a time period of a week or more; a week from Monday will be too soon!. weekend-a time period usually extending from Friday night through Sunday; more loosely defined as any period of successive days including one and only one Sunday.