Onomatopoeia

n.

The use of words that mimic the sounds that they are associated with. For example "meow" is an onomatopoeic word referring to the sound made by cats. Sounds that are not proper words are not onomatopoeic, for example "brrrr" (sound commonly made when a person is cold).

Commonly used as sound effect in manga and comics.

Onomatopoeic / onomatopoetic adj.
Onomatopoeically / Onomatopoetically adv.