The definition of unlikely is something that is probably not going to happen or that has a very slim chance of occurring.(adjective)
The chance of snow in June in Florida is an example of something that would be described as unlikely.
See unlikely in Webster's New World College Dictionary
Origin: ME unlikly, prob. based on ON ūlīkligr
See unlikely in American Heritage Dictionary 4
adjective un·like·li·er, un·like·li·est
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