To fall sick; fall into ill health; become ill: used of persons, animals, or plants: as, the fowl sickened; the vine sickened.To experience a sickening sensation; feel nauseated or disgusted: as, to sicken at the sight of squalor.To lose force or vitality; become weakened, impaired, or deteriorated: said of things (in technical use, especially of mercury: compare mortification, 1 ).To make sick; bring into a disordered state or condition; affect with disease, or (more commonly) with some temporary disorder or indisposition, as nausea, vertigo, or languor: as, the bad odors sickened him.To make mentally sick; cause to feel nauseating contempt or disgust. See sickening.To make nauseatingly weary (of) or dissatisfied (with); cause a disgusted dislike in: with of: as, this sickened him of his bargain.To bring into an unsettled or disordered state; impair; impoverish: said of things.