Dictionary:

mononuclear

  (mŏn'ō-nū'klē-ər, -nyū'-)

1. Having only one nucleus: a mononuclear cell.
2. Chemistry. Monocyclic.

Having only one nucleus.

Having only one nucleus.

• blockade of m.–phagocytic system — results when large numbers of particles or bacteria absorb all available receptor sites or otherwise interfere with phagocytosis. May be a factor in reducing host defense mechanisms.
• m. phagocytes — macrophages.
• m. phagocyte system — the group of highly phagocytic cells that have a common origin from stem cells of the bone marrow and develop circulating monocytes and tissue macrophages, which develop from monocytes that have migrated to connective tissue of the liver (Kupffer's cells), lung, spleen and lymph nodes. The term has been proposed to replace reticuloendothelial system, which includes some cells of different origin.

The adjective has one meaning:

Meaning #1: (biology) having only one nucleus
  Synonym: mononucleate
  Antonyms: binucleate (meaning #1), trinucleate (meaning #1)