Referring to a negatively charged ion.
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an·ion·ic .an-(.)ī-'än-ik adj
1) of or relating to anions
2) characterized by an active and esp. surface-active anion
an·ion·i·cal·ly -i-k(ə-)lē adv
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an·ion·ic (an″i-onґik) pertaining to or containing an anion.Medical dictionary. 2011.