Free, unconfined, especially not confined in prison, as in To our distress, the housebreakers were still at large. [1300s]

At length, fully; also, as a whole, in general. For example, The chairman talked at large about the company's plans for the coming year, or, as Shakespeare wrote in Love's Labour's Lost (1:1): “So to the laws at large I write my name” (that is, I uphold the laws in general). This usage is somewhat less common. [1400s]

Elected to represent an entire group of voters rather than those in a particular district or other segment—for example, alderman at large, representing all the wards of a city instead of just one, or delegate at large to a labor union convention. [Mid-1700s]

A descriptive term for the election of public officials by an entire governmental unit rather than by subdivisions of the unit. For example, a delegate at large does not represent any specific district or locale, but speaks instead for a much wider group of people.