n 1  :  the act of retaining: as  a  :  abnormal retaining of a fluid or secretion in a body cavity < of urine>  < of bile>   b  :  the holding in place of a tooth or dental replacement by means of a retainer < is the fixation of a removable partial denture in the mouth in such a manner that … it may be inserted and retained with sufficient firmness -Rev. of Dentistry>   2  :  a preservation of the aftereffects of experience and learning that makes recall or recognition possible .
 
 
 
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