1. The ordinal number of one thousand in counting order
   - 1000th

1. Position 1,000 in a countable series of things
   "The thousandth customer received a special prize"
    
2. One part in a thousand equal parts
   "A millisecond is one-thousandth of a second";
   - one-thousandth

Derived forms: thousandths

See also: ordinal

Type of: common fraction, rank, simple fraction, vulgar fraction [Brit]

Encyclopedia: Thousandth