1.nounA mythological shield associated with the Greek deities Zeus and Athena (and their Roman counterparts Jupiter and Minerva) shown as a short cloak made of goatskin worn on the shoulders, more as an emblem of power and protection than a military shield. The aegis of Athena or Minerva is usually shown with a border of snakes and with the head of Medusa in the center.
2.nounUsually as under the aegis: guidance, protection; endorsement, sponsorship.