adjective
 last in order of a series of a thousand.
 being one of a thousand equal parts.
noun
 a thousandth part, especially of one (1/1000).
 the thousandth member of a series.
 Also thousandth’s place. (in decimal notation) the position of the third digit to the right of the decimal point.
adjective
 (usually prenominal)
 being the ordinal number of 1000 in numbering or counting order, position, time, etc
 (as noun)the thousandth in succession
noun

 one of 1000 approximately equal parts of something
 (as modifier)a thousandth part
 one of 1000 equal divisions of a particular scientific quantitymillivolt Related prefix: milli
 the fraction equal to one divided by 1000 (1/1000)
adj.1550s, from thousand + th (1).