(1) (botany) The state of efflorescing; time of flowering or blossoming; anthesis.
(2) (medicine) A condition where there is skin reddening, a rush or an eruption on the skin, e.g. measles, smallpox, scarlatina, etc.
(3) (chemistry) The formation of salt crystals on a surface by the spontaneous loss of water (as vapor) from the hydrated crystalline solid.
(4) (chemistry) The deposit or crust that results from the process of efflorescing.
(5) The process of efflorescing.
In chemistry, an example of efflorescence is when a gypsum is exposed to a dry environment it will lose its water by evaporation and form a solid crust, anhydrite, on the surface.
Word origin: Latin efflorescere (to bloom, blossom).