Crossword clues for mastocyte mastocyte A large connective tissue cell that contains histamine and heparin and serotonin which are released in allergic reactions or in response to injury or inflammation Wiktionary mastocyte n. mast cell. WordNet mastocyte n. a large connective tissue cell that contains histamine and heparin and serotonin which are released in allergic reactions or in response to injury or inflammation [syn: mast cell, labrocyte]