The definition of chubby is someone plump, rounded or slightly overweight.(adjective)
When you have a toddler who is round and plump, this is an example of someone who would be described as chubby.
See chubby in Webster's New World College Dictionary
See chubby in American Heritage Dictionary 4
adjective chub·bi·er, chub·bi·est
Origin: Probably from chub (from the plumpness of the fish).
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