Being the only one of its kind; unequaled, unparalleled or unmatched.
Of a rare quality, unusual.
Of a feature, such that only one holder has it.
Particular, characteristic.
A thing without a like; something unequalled or unparallelled; one of a kind.
Not noble; ignoble; base.
Of a metal, being at the lower end of the electrochemical series, i.e. oxidising readily.
To make (someone or something) no longer noble