Onomatopoeia is a word in English that describes words that phonetically resemble or recall the sound that they describe. The clearest examples of these are animal sounds, such as "oink" or "meow"
The word onomatopoeia derives from Greek, and its original meaning differs from English because it means "making or creating names". Therefore, the word originally refers to the act of creation of words resembling their described sounds.
The pronunciation of onomatopoeia is oh-nuh-mah-tuh-PEE-uh.
The key to pronouncing onomatopoeia correctly is how you pronounce the vowels where you place the stress. Some of the vowels are not pronounced as they appear. For example, in the second syllable, the "o" is pronounced with a short "u", which means with an "uh" sound. The "uh" sound also substitutes the vowels in the last syllable.
The stress is placed on the "poe", which is pronounced as -PEE, with a long "e" or "ee" sound.
It is also worth noting that pronunciation of onomatopoeia is the same in both American and British English, where the only variation is given by the accent of the speaker.