adj. 1. Being in the process of passing out of use or usefulness; becoming obsolete. 2. Biology Becoming reduced during the course of evolution; vestigial or nearly vestigial. Used of an organ or other part of an organism. [Latin obsolēscēns, obsolēscent-, present participle of obsolēscere, to fall into disuse : ob-, away; see OB- + solēre, to be accustomed to.] ob′so·lescence n. ob′so·lescent·ly adv. |
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