plasma celln. Any of various short-lived cells that develop from activated B cells and secrete large numbers of antibodies. They are found chiefly in the bone marrow, spleen, and lymph nodes. Also called plasmacyte.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.plas?ma cell` n. an antibody-secreting cell, derived from B cells, that plays a major role in antibody-mediated immunity. Also called plas?ma?cyte (?plæz m??sa?t) [1885?90] Random House Kernerman Webster’s College Dictionary, © 2010 K Dictionaries Ltd. Copyright 2005, 1997, 1991 by Random House, Inc. All rights reserved.plasma cell A cell that produces antibodies as part of an immune response. B cells develop into plasma cells. See Note at antibody.The American Heritage® Student Science Dictionary, Second Edition. Copyright © 2014 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.