Merriam-Webster Collegiate Dictionary - throughout

 I. adverb  Date: 13th century  1. in or to every part ; everywhere of one color ~  2. during the whole time or action ; from beginning to end remained loyal ~  II. preposition  Date: 13th century  1. all the way from one end to the other of ; in or to every part of cities ~ the United States  2. during the whole course or period of troubled her ~ her life