From Middle English thousendfold, from Old English þūsendfeald, from Proto-Germanic *þūsundīfalþaz, corresponding to thousand +‎ -fold. Cognate with Dutch duizendvoud, duizendvoudig, German tausendfältig, Danish tusindfold, Swedish tusendfalt, tusendfaltig, Icelandic þúsundfalt.

• (UK) IPA^(key): /ˈθaʊzəndfəʊld/
• (General American) IPA^(key): /ˈθaʊzəndfoʊld/

thousandfold (not comparable)

1. Multiplied by one thousand (1000), repeated a thousand times.

   The changes to the algorithm resulted in a thousandfold increase in efficiency, earning the engineer a small brass plaque.

   • 1857, [Thomas Hughes], “The War of Independence”, in Tom Brown’s School Days.[…], Cambridge, Cambridgeshire: Macmillan & Co., →OCLC, part I, page 185:

     [T]he fresh brave school-life, so full of games, adventures, and good fellowship, so ready at forgetting, so capacious at enjoying, so bright at forecasting, outweighed a thousandfold their troubles with the master of their form, and the occasional ill-usage of the big boys in the house.

2. Having one thousand parts or members.
   • 1851 November 14, Herman Melville, “Knights and Squires”, in Moby-Dick; or, The Whale, 1st American edition, New York, N.Y.: Harper & Brothers; London: Richard Bentley, →OCLC, page 125:

     Looking into his eyes, you seemed to see there the yet lingering images of those thousand-fold perils he had calmly confronted through life.

thousandfold (not comparable)

1. By a factor of a thousand.