Onomatopoeia refers to words that imitate the sounds they describe.
So, onomatopoeic means "relating to or characterized by onomatopoeia." It describes something that uses words that sound like the noises they represent.
For example:
* The onomatopoeic word "buzz" imitates the sound of a bee.
* The onomatopoeic sound effect "crash" represents the sound of something breaking.
Essentially, onomatopoeic means something is sound-imitative or mimicking sounds.