Real Dictionary

peripheral
(of a cell) having only one nucleus [...]
a part of an organism consisting of a large number of cells having a similar structure and function [...]
a reddish fluid in vertebrates that is pumped by the heart through the arteries and veins, supplies tissues with nutrients, oxygen, etc, and removes waste products. It consists of a fluid (see blood plasma) containing cells (erythrocytes, leucocytes, and
a small simple room, as in a prison, convent, or monastery; cubicle [...]
a type of white blood cell formed in lymphoid tissue [...]
any of the various large unpigmented cells in the blood of vertebrates [...]
not relating to the most important part of something; incidental, minor, or superficial [...]
adjective: A peripheral activity or issue is one which is not very important compared with other activities or issues.