An ideophone is any word in a certain word class evoking ideas in sound imitation (onomatopoeia) to express an action, manner, or property. The class of ideophones is the least common cross-linguistically; it occurs mostly in African, Australian, and Amerindian languages, and sporadically elsewhere. It is globally the only known word class exotic to English. Ideophones resemble interjections but are unclassifiable as such owing to their special phonetic or derivational characteristics, and based on their syntactic function within the sentence. They may include sounds that deviate from the language's phonological system, imitating—often in a repetitive manner—sounds of movement, animal noises, bodily sounds, noises made by tools or machines, and the like.
While English does have ideophonic or onomatopoetic expressions, it does not contain a proper class of ideophones because any English onomatopoeic word can be included in one of the classical categories. For example, la-di-da functions as an adjective while others, such as zigzag, may function as a verb, adverb or adjective, depending on the clausal context. In the sentence 'The rabbit zigzagged across the meadow", the verb zigzag takes the past –ed verb ending. In contrast, the reconstructed example *"The rabbit zigzag zigzag across the meadow" emulates an ideophone but is not idiomatic to English.
Dictionaries of languages like Japanese, Korean, Xhosa, Yoruba, and Zulu list thousands of ideophones. Sometimes ideophones are called phonosemantic to indicate that it is not a grammatical word class in the traditional sense of the word (like verb or noun), but rather a lexical class based on the special relationship between form and meaning exhibited by ideophones. In the discipline of linguistics, ideophones have sometimes been overlooked or treated as a subgroup of interjections.
The word ideophone was coined in 1935 by Clement Martyn Doke, who defined it in his Bantu Linguistic Terminology as follows.
A vivid representation of an idea in sound.