noun
also log ship
: a thin flat usually triangular piece of wood that is typically like a quadrant of a circle and that usually has a radius of 5 or 6 inches and is loaded with lead on the arc so as to float point up and that is attached to a log line by cords from each corner and is tossed into the water so that the log line may run out from the log reel when the motion of a ship through the water or the velocity of a current is being gauged