wa·ter·shed 
(wôtər-shĕd′, wŏtər-)
(wôtər-shĕd′, wŏtər-)n.
1. The entire region draining into a river, river system, or other body of water: a list of reptiles found in the watershed. Also called basin, drainage basin.
2. A ridge of high land dividing two areas that are drained by different river systems. Also called divide, water parting.
3. A critical point that marks a division or a change of course; a turning point: "a watershed in modern American history, a time that ... forever changed American social attitudes" (Robert Reinhold).
[Probably translation of German Wasserscheide, water parting, border between watersheds : Wasser, water + Scheide, divide, parting.]
- authority
- authorization
- authorize
- Authorized Version
- authorizer
- authorship
- autism
- autism spectrum
- autism spectrum disorder
- autist
- autistic
- autistically
- autistic savant
- auto
- auto-
- autoantibody
- autoantigen
- autobahn
- autobiographer
- autobiographic
- autobiographical
- autobiographically
- autobiography
- autobus
- autocatalysis