Is it ensure, insure, or assure?
unsaturated un·sat·u·rat·ed (ŭn-sāch'ə-rā'tĭd)
Of or relating to a solution in which the solvent is capable of dissolving still more of the solute; not saturated.
Of or relating to a chemical compound in which all the affinities are not satisfied, so that still other atoms or radicals may be added to it.
Of or relating to chemical compounds containing double and triple bonds.