What is either half of a square-rigged vessel's yard, from the center or mast to the end. Note: Ships are said to be yardarm and yardarm when so near as to touch, or interlock yards called?

yardarm — Either half of a square-rigged vessel's yard, from the center or mast to the end. Note: Ships are said to be yardarm and yardarm when so near as to touch, or interlock yards. (Webster's 1913.)