Definition of special session in US English:

special session

noun

  • 1British (chiefly in plural) a periodic meeting of justices of the peace, convened by statute to address a particular kind of business (now historical); occasionally with singular concord.

  • 2A session of a legislative or regulatory body, convened outside the regular schedule in order to address urgent business.

Origin

Late 16th century; earliest use found in William Lambarde (1536–1601), antiquary and lawyer.