1.NounThe quality or state of being sick or diseased; illness; an illness.
2.NounNausea; qualmishness; as, sickness of stomach.
3.NounThe analogical misuse of a rarer or marked grammatical case in the place of a more common or unmarked case. (Can we verify this sense, particularly "Does this exist outside of the phrase dative sickness with reference to the Icelandic language?)"?)