WordNet (r) 3.0 (2006):

saturation point
    n 1: (chemistry) the stage at which a substance will receive no
         more of another substance in solution or in a vapor

Moby Thesaurus II by Grady Ward, 1.0:

46 Moby Thesaurus words for "saturation point":
   activity, amplitude, artificial radioactivity, bellyful,
   congestion, contamination, curiage, decontamination, engorgement,
   fallout, fill, flood tide, full, fullness, glut, half-life,
   high tide, high water, impletion, more than enough,
   natural radioactivity, nuclear radiation, overfullness, plenitude,
   plethora, radiant energy, radiation, radioactive radiation,
   radioactivity, radiocarbon dating, radiolucency, radiopacity,
   radiosensibility, radiosensitivity, repletion, satiation, satiety,
   satisfaction, saturatedness, saturation, skinful, snootful,
   specific activity, spring tide, supersaturation, surfeit