What does the word unknown mean?

Usage examples for unknown

  1. 326; cause of it unknown, ii. – Rousseau Volumes I. and II. by John Morley
  2. That is indeed true; but I find no hint of who this unknown woman was. – A Life of St. John for the Young by George Ludington Weed
  3. " But," he answered earnestly, " unknown to myself her vision must always have been here." – Dross by Henry Seton Merriman