semibreve rest

from Wiktionary, Creative Commons Attribution/Share-Alike License.

• noun music A semibreve rest is a pause or interval of silence equal in duration to two half rests or one half of a breve rest. In common or 4/4 time, its duration is four beats.
• noun music A symbol used in musical notation drawn as a solid rectangle directly below the line above the middle line of a staff whose height is half the distance between lines.