Verb
(transitive) To cause to become less saturated or unsaturated.
To lessen the saturation of (a colour).
(chemistry) To convert (a saturated compound) to an unsaturated one.
(intransitive) To become less saturated or unsaturated.
(of a colour) To decrease in saturation.
(medicine) Of the oxygen saturation level in one's hemoglobin: to decrease, to drop.
(medicine, of a person) To undergo a decrease in the oxygen saturation level in the hemoglobin.
Source: en.wiktionary.org