(1) A word or phrase (such as "buzz" and "cock a doodle doo") that imitates the sound associated with the object or action it refers to: an onomatope. See also:reduplicative.
(3) A word or phrase that recurs in a sentence or paragraph. See also:
Examples and Observations (#1 and #2):
"Sound alone is the basis of a limited number of words, called echoic or onomatopoeic, like bang, burp, splash, tinkle, bobwhite, and cuckoo. Words that are actually imitative of sound, like meow, bowwow, and vroom--though these differ from language to language--can be distinguished from those like bump and flick, which are called symbolic. Symbolic words regularly come in sets that rime (bump, lump, clump, hump) or alliterate (flick, flash, flip, flop) and derive their symbolic meaning at least in part from other members of their sound-alike sets. Both imitative and symbolic words frequently show doubling, sometimes with slight variation, as in bowwow, choo-choo, and pe(e)wee."
(John Algeo and Thomas Pyles, The Origins and Development of the English Language, 5th ed. Thomson Wadsworth, 2005)
Examples and Observations (#3)
"Repetitions help to echo key words, to emphasize important ideas or main points, to unify sentences, or to develop coherence among sentences. Skillful repetitions of important words or phrases create 'echoes' in the reader's mind: they emphasize and point out key ideas. You can use these 'echo words' in different sentences--even in different paragraphs--to help 'hook' your ideas together. . . .
"[E]cho words may come any place in the sentence: with the subjects or the verbs, with the objects or the complements, with prepositions or other parts of speech. You need not always repeat the word exactly; think of other forms the word may take, such as freak, freakiness, freakishness (nouns), freaking (participle), freaky and freakish (adjectives), and freakishly and freakily (adverbs)."
(Ann Longknife and K. D. Sullivan, The Art of Styling Sentences, 4th ed. Barron's, 2002)