\Thou"sandth\, a.
1. Next in order after nine hundred and ninty-nine; coming
   last of a thousand successive individuals or units; -- the
   ordinal of thousand; as, the thousandth part of a thing.
2. Constituting, or being one of, a thousand equal parts into
   which anything is divided; the tenth of a hundredth.
3. Occurring as being one of, or the last one of, a very
   great number; very small; minute; -- used hyperbolically;
   as, to do a thing for the thousandth time.

\Thou"sandth\, n.
The quotient of a unit divided by a thousand; one of a
thousand equal parts into which a unit is divided.