quarter-deck—the part of the upper deck between main-mast and stern.
petty officer—a non-commissioned officer.
the spokesman of the envious children of Jacob . . . of young Joseph—This allusion from the Bible (Genesis 37:31–33) connects Claggart’s deceitful act with that of the liar who convinced Jacob that a wild beast had devoured Joseph, his youngest and favorite son.
the wind in the cordage—the sound of the wind passing through the ropes.
the waist—the middle portion of the ship.
