At Large Meaning

(US, politics, of an election) Having an electorate across multiple districts.

Example:   For a nervous twenty-four hours, three wanted criminals were at large in the city.
  The ambassador-at-large was designated to the Middle East as a region, rather than to a specific country.
1621, Robert Burton, The Anatomy of Melancholy, vol.I, New York 2001, p.236:
  The like example I find in Lælius à Fonte Eugubinus, consult. 129 […]. Read in him the story at large.
In general; as a whole.
  Some people support the measure, but the community at large will probably be against it.
  The city has five city council districts; however, the mayor is elected at large.