What is the meaning of "wobbly"
Is it the right word to express the little shakeness of jelly?
As far as I check up with the dictionary, the word "wobble" is to express "unstableness." or so.

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You can use the word to describe jello (maybe not jelly). Usually the word "wobbly" reminds me of someone who has had one too many beers to drink. His or her legs are wobbly or unsteady.

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This is all correct.  
A wobble can be in a desk, a chair, a walk, ribber material, jelly - it is a wiggle or a loosness.

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FYI  http://www.urbandictionary.com/define.php?term=woobly

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