noun
non-permanent member of the UN Security Council
Refers specifically to the ten elected members of the United Nations Security Council that serve two-year terms, as opposed to the five permanent members.
日本は何度も非常任理事国に選ばれている。
Japan has been elected as a non-permanent member of the Security Council many times.
常任理事国 refers to the five permanent members of the UN Security Council (US, UK, France, Russia, China), while 非常任理事国 refers to the ten non-permanent members elected for two-year terms.
Compound of 非 (hi, 'non-'), 常任 (jōnin, 'permanent'), 理事 (riji, 'director; council member'), and 国 (koku, 'country').