Other forms: left wings
The left wing is the group of voters and politicians who lean toward liberal, progressive, socialist, or radical political beliefs. Generally, the left wing advocates for social equality and bigger government.
The term left wing has different meanings in different parts of the world, but most people in the US understand it to mean "liberal" or "progressive." As well as a noun that encompasses a group of like-minded people, you can use it as an adjective describing these beliefs: "The left wing activists rallied against the governor's cuts to social services." This term was first used to mean "the left side of an army."