in the retina
of the eye
The rod is an Imperial unit of length, also known as the pole or perch. It is equal to 5.5 yards or 16.5 feet; 5.029 metres.
The rod is supposedly a species of creature that flits about in the air at such a high speed as to not be seen by the naked eye, but which can be caught on video. See: Rod (cryptozoology).
is a straight and slender stick; a wand; hence, any slender bar, as of wood or metal (applied to various purposes).