Definition of "at one"

at one

prepositional phrase
1. (often with with) In harmony or unity.
2. (often with with) In agreement, unanimous, of the same opinion.
  Quotations
  The pastoral deity to whom they paid their devotions was Pales, as to whose sex the ancients themselves were not at one.
  1890, James George Frazer, The Golden Bough, volume 2, page 326
  Vidal's old antagonist Norman Mailer was largely at one with him on this, jauntily alleging that endless war was the only way to vindicate the drooping virility of the traditional white American male.
  2010, Christopher Hitchens, Hitch-22, Atlantic, published 2011, page 245
3. (archaic) Into a state of harmony, friendship or reconciliation.
  Quotations
  And the next daye he shewed himsilfe unto them as they strove, and wolde have sett them at one agayne saynge: Syrs ye are brethren why hurte ye won another?
  1526, [William Tyndale, transl.], The Newe Testamẽt […] (Tyndale Bible), [Worms, Germany: Peter Schöffer], Acts ]