'Concubines' in the Bible

And David took him more concubines and wives out of Jerusalem, after he was come from Hebron: and there were yet sons and daughters born to David.

And the king went forth, and all his household after him. And the king left ten women, which were concubines, to keep the house.

And Ahithophel said unto Absalom, Go in unto thy father's concubines, which he hath left to keep the house; and all Israel shall hear that thou art abhorred of thy father: then shall the hands of all that are with thee be strong.

So they spread Absalom a tent upon the top of the house; and Absalom went in unto his father's concubines in the sight of all Israel.

And Joab came into the house to the king, and said, Thou hast shamed this day the faces of all thy servants, which this day have saved thy life, and the lives of thy sons and of thy daughters, and the lives of thy wives, and the lives of thy concubines;

And David came to his house at Jerusalem; and the king took the ten women his concubines, whom he had left to keep the house, and put them in ward, and fed them, but went not in unto them. So they were shut up unto the day of their death, living in widowhood.