A geometrical shape with 18 even (equal) sides
http://wiki.answers.com/Q/What_is_a_18_gon

1. Write the following expression for exterior angles  (number of exterior angles)angle measurement) = 360 degrees. 2. Substitute "18" for "number of exterior angles
http://www.ehow.com/how_8781304_exterioranglereg...

There no official shape but it would have 18 sides.
http://www.chacha.com/question/howmanysidesdoes...

Sum of exterior angles of all ngons is 360. So in a regular 18gon, each exterior angle = 360/18 = 20. each interior angle = 18020 = 160. Sum of all interior angles = 18*160 = 2880
http://answers.yahoo.com/question/index?qid=201002...
