SAO

noun3

1. •
   Initialism of session-at-once, a recording mode for optical discs.
2. •
   Initialism of school attendance order.
3. •
   (UK) Initialism of Specified Associated Organisation.

noun1

1. •
   (rare) Any marine annelid of the genus Hyalinoecia, especially Hyalinoecia tubicola of Europe, which inhabits a transparent movable tube resembling a quill in color and texture.