rod

Concise Oxford English Dictionary © 2008 Oxford University Press:
rod/rɒd/

▶noun

• 1 a thin straight bar, especially of wood or metal.

• 2 a fishing rod.

• 3 a slender straight stick or shoot growing on or cut from a tree or bush.

  ■ (the rod) the use of a stick for caning or flogging.

• 4 historical, chiefly Brit. another term for perch3 (sense 1).

  ■ (also square rod) another term for perch3 (sense 2).

• 5 US informal a pistol or revolver.

• 6 Anatomy one of two types of light-sensitive cell present in the retina of the eye, responsible mainly for monochrome vision in poor light. Compare with cone (sense 3 of the noun).

– phrases
make a rod for one's own back do something likely to cause difficulties for oneself later.
rule someone/thing with a rod of iron control or govern someone or something very harshly.

– derivatives
rodless adjective,
rodlet noun,
rod-like adjective.

– origin OE rodd; prob. rel. to ON rudda ‘club’.