noun
Refers to a political party other than the two largest or dominant parties in a system, often used in discussions of elections and parliamentary politics.
選挙では第三政党が議席を伸ばした。
In the election, the third party increased its seats.
二大政党の対立に飽きた有権者が第三政党に流れた。
Voters tired of the two major parties' conflict shifted to a third party.
Compound of 第三 (third) and 政党 (political party). The term is a straightforward modern political term with no obscure historical derivation.