From WordNet (r) 2.0 (August 2003) [wn]:
1000
adj : denoting a quantity consisting of 1,000 items or units [syn:
thousand, a thousand, one thousand, m, k]
n : the cardinal number that is the product of 10 and 100 [syn:
thousand, one thousand, M, K, chiliad, G,
grand, thou, yard]
From The Collaborative International Dictionary of English v.0.48 [gcide]:
1000 \1000\ adj.
1. denoting a quantity consisting of one more than nine
hundred ninety nine and one less than one thousand and
one; -- representing the number one thousand as Arabic
numerals
Syn: thousand, a thousand, one thousand, m, k
[WordNet 1.5 +PJC]