1. Pantoum

2. Definition
Pantoum: (noun) a Malay verse form consisting of an indefinite number of quatrains with the second and fourth lines of each quatrain repeated as the first and third lines of the following one.
(dictionary.com)

3. Better definition of Pantoum:
A poem that has the second and fourth lines of one stanza repeating as the first and third line in the next stanza.
Better definition of Pantoum:

4. As she dances on the moonlit glen Taking in the freshness of the air She is alone, but not lonely She is surrounded by spirits Searching again for her silent companions They watch the contentment she holds
Example of a Pantoum
Red: The second and fourth lines 0f the first stanza will become first and third in the second stanza.
Blue: The second and fourth lines of the second stanza will become first and third lines of the last stanza.