A Cinquain is a very unique five-line poem with an elaborate structure. In the first line you can write one noun, which is usually the thing or person the poem is about. In the second line you will write two adjectives to describe that noun. In the third line you'll write three verbs related to the noun in line1. In line 5 you will sum up the poem with a synonym of the noun in line one or with a related noun. Here's a very comprehensive example of a Cinquain about triangles:
'Triangles
Pointy edges
Revolving, rotating, angling
Triangles are all different.
180o'
Pointy edges
Revolving, rotating, angling
Triangles are all different.
180o'
