1610s, from un- (1) "not" + alterable. Related: Unalterably.
He reach'd a middle height, and at the stars,
Which are the brain of heaven, he look'd, and sank.
Around the ancient track march'd, rank on rank,
The army of unalterable law.
[George Meredith, "Lucifer in Starlight"]
unalterable resolve
an unalterable ground rule
an unalterable death sentence
unaffected
unafraid
unaided
unalienable
unalloyed
unalterable
unaltered
unambiguous
un-American
unanimity
unanimous
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