thal·as·se·mi·a (th?l??-s??m?-?)n. An inherited form of anemia occurring chiefly among people of Mediterranean descent, caused by faulty synthesis of part of the hemoglobin molecule. Also called Mediterranean anemia.[Greek thalassa, sea + -emia.]thal?as·se?mic adj.American Heritage® Dictionary of the English Language, Fifth Edition. Copyright © 2016 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.thal?as?se?mi?a (??æl ??si mi ?) n. a hereditary anemia marked by the abnormal production of hemoglobin, occurring chiefly in people of Mediterranean origin. [1932;