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1.
Why the fuck are you searching this on Urban Ditionary, You got problems!!

The relatively close juxtaposition of the same or similar vowel sounds, but with different end consonants in a line or passage, thus a vowel rhyme, as in the words, date and fade.
example of assonance "that dolphin-torn, that gong-tormented sea"
by Varun.B.S May 07, 2006
 
2.
Literally means "Ass sounds" or sounds emitted from the ass.
I had beans and dark beer for lunch and everyone was getting sick of my assonance.

The resonating sound emitting from his ass is called assonance.
by McCrazy October 10, 2007