It is "assonance":
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assonance
in prosody, repetition of stressed vowel sounds within words with different end consonants, as in the phrase "quite like." It is unlike rhyme, in which initial consonants differ but both vowel and end-consonant sounds are identical, as in the phrase "quite right." Many common phrases, such as "mad as a...
• assonance
Resemblance or correspondence in sound. hEnglish - advanced version
• assonance
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assonance
\as"so*nance\ (&?

, n. [cf. f. assonance. see assonant.]
1. resemblance of sound. "the disagreeable assonance of ?'sheath' and ?'sheathed.'" --steevens.
2. (pros.) a peculiar species of rhyme, in which the last acce`ted vow`l and tnose whioh follow it in one word correspond in sound with the vowels of another word, while the consonants of the two words are unlike in sound; as, calamo and platano, baby and chary. the assonance is peculiar to the spaniard.
3. incomplete correspondence. assonance between facts seemingly remote.
assonance
n : the repetition of similar vowels in the stressed syllables of successive words [syn: vowel rhyme]
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WordNet 2.0
• assonance
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Noun
1. the repetition of similar vowels in the stressed syllables of successive words
(synonym) vowel rhyme
(hypernym) rhyme, rime
(derivation) assonate