Onomatopoeia is usually defined as the creation or use of words that sound like the items or actions they name or refer to. As such, it is a rhetorical device: a language technique or device used to create an effect in or for the reader. It differs from cacophony, the intentional use of harsh sound for effect, as well as from euphony, the use of harmonious sounds, also for effect, although onomatopoeia may, depending on the item or action being imitated, fit into either of those categories.
Although the term in this sense covers a wide range of sounds, many of the words it includes seem to fall into a few categories, with the most, by far, being associated with the sounds made by animals. Here are some onomatopoetic words, grouped by category:
Mechanical. Machine noises seem to make up a fair amount of the common words in this group. Examples include buzz, beep, whirr, click, clack, clunk, clatter, clink. Many of these words begin with a "cl" sound.
Fast Motion. Words that convey the sound of speed seem often to begin with the letter s or z. Boing, varoom/vroom, whoosh, swish, swoosh, zap, zing, zip, and zoom are examples.
Musical. Some words in this group are associated with specific music instruments — the twang of a banjo or guitar, for example, or oompah for a tuba, or plunk for a keyboard. Others imitate a metallic sound, and these often end in ng: ting, ding, ring, ping, clang, bong, brrrring, jingle, and jangle. Then there are some that clearly evoke wind instruments, like blare, honk, and toot; and another group that seem percussive, like rap, tap, boom, rattle, and plunk. A person making music without an instrument might hum or clap or snap.
Food Preparation and Eating. In cooking, food may crackle or sizzle and oil may splatter. When a person pours something to drink, it may go splash, kerplunk, or gush, but hopefully it won’t drip, and when we open a soft drink, it will probably fizz. When it’s time to eat, people are likely to nibble, munch, gobble, and crunch.
Fighting. The action words that show up in comic books during fighting scenes are onomatopoetic, and include terms like pow, bif, bam, whomp, thump, smash, zowie, bang, and wham are some of them.
Animals. The sounds that animals make are complicated even in English, but it’s important for people to be aware that — contrary to what they might expect — in different parts of the world, the words used for animal sounds are quite different. Sheep do not universally go baa, nor do ducks quack everywhere in the world. Here are some common English renderings:
Onomatopoeia is also used to refer to imitative resonances of other kinds. In this meaning, using a little word like wee to mean small, or a long or big word like macroscopical to mean large, is an example of onomatopoetic usage. It can also involve shape, such as when a poem about a tree is written to appear in the shape of the tree.