The Collaborative International Dictionary of English v.0.48:

Tripoli \Trip"o*li\, n. (Min.)
   An earthy substance originally brought from Tripoli, used in
   polishing stones and metals. It consists almost wholly of the
   siliceous shells of diatoms.
   [1913 Webster]

WordNet (r) 3.0 (2006):

tripoli
    n 1: a weathered and decomposed siliceous limestone; in powdered
         form it is used in polishing [syn: rottenstone,
         tripoli]
    2: the capital and chief port and largest city of Libya; in
       northwestern Libya on the Mediterranean Sea; founded by the
       Phoenicians in the 7th century BC [syn: Tripoli, Tarabulus
       Al-Gharb, capital of Libya]
    3: a port city and commercial center in northwestern Lebanon on
       the Mediterranean Sea [syn: Tarabulus, Tripoli,
       Tarabulus Ash-Sham, Trablous]

U.S. Gazetteer Places (2000):

Tripoli, IA -- U.S. city in Iowa
   Population (2000):    1310
   Housing Units (2000): 561
   Land area (2000):     1.401547 sq. miles (3.629990 sq. km)
   Water area (2000):    0.000000 sq. miles (0.000000 sq. km)
   Total area (2000):    1.401547 sq. miles (3.629990 sq. km)
   FIPS code:            78915
   Located within:       Iowa (IA), FIPS 19
   Location:             42.805736 N, 92.257580 W
   ZIP Codes (1990):     50676
   Note: some ZIP codes may be omitted esp. for suburbs.
   Headwords:
    Tripoli, IA
    Tripoli