There are three main words in Japanese that describe onomatopoetic constructs:

擬音語 [ぎおんご] – onomatopoeia

• 擬 [ギ・まがい・もどき] – mimic; imitate
• 音 [オン・おと] – sound; noise
• 語 [ゴ・かたる] – word; language

Examples:

• ドキドキ – being nervous, excited, or surprised; a heartbeat (“pitter pat”)
• ガチャン – breaking glass
• ドカン – an explosion or crash

擬声語 [ぎせいご] – onomatope (i.e. imitative or onomatopoetic word); phonomime

• 擬 [ギ・まがい・もどき] – mimic; imitate
• 声 [セイ・こえ] – voice
• 語 [ゴ・かたる] – word; language

Examples:

• ワンワン – dog (“bow wow”)
• メーメー – sheep (“baaaaa”)
• ブーブー – pig (“oink”)

Strictly speaking, only 擬音語 (onomatopoeia) and 擬声語 (phonomimes) are onomatopoeia as the word is used in English, as they mimic sounds that are actually made by animals, people, and things.

But Japanese also has another word to describe mimesis:

擬態語 [ぎたいご] – mimetic word; a word that mimics something that does not make a sound; phenomime

• 擬 [ギ・まがい・もどき] – mimic; imitate
• 態 [タイ・わざと] – attitude; condition; appearance
• 語 [ゴ・かたる] – word; language

Examples:

• しいん – silence; quiet  (My ex-girlfriend used to say this to me any time one of my jokes bombed in Japanese.  In the US, we will sometimes make cricket noises.)
• ばらばら – scattered about
• たっぷり – plenty

Finally, there’s also something called 音喩 [おんゆ] (sound-metaphor) which is used to describe made-up sounds and actions in 漫画 [まんが] (manga – Japanese comics) that don’t exist in standard Japanese.

In the future, I’ll introduce you to other onomatopoeia under the category 擬音語.