According to Wikipedia, is a poetic form based on the Fibonacci series (counting syllables). “The typical fib is a six line, 20 syllable poem with a syllable count by line of 1/1/2/3/5/8.”

The example given (written by Gregory K. Pincus) is helpfully self-reflexive:

One
Small,
Precise,
Poetic,
Spiraling mixture:
Math plus poetry yields the Fib.