1
general::
Phrase(s): *as one
as if acting or moving as a single person. (*Typically: act ~; move ~; speak ~.) • All the dancers moved as one. • The chorus spoke as one.
McGrawhill's American Idioms And Phrasal Verbs
2
general::
Also, as one man or woman. All together, unanimously. For example, The marchers shouted as one, "We shall overcome!" or They replied as one woman, "Of course we'll stay and help." This term appeared in the Bible (Judges 20:8): "And all the people arose as one man.'' [Late 1500s] For synonyms, see TO A MAN; WITH ONE VOICE.
American Heritage Idioms