from The American Heritage® Dictionary of the English Language, 4th Edition

  • n. The haploid nucleus of a sperm or egg before fusion of the nuclei in fertilization.

from Wiktionary, Creative Commons Attribution/Share-Alike License

  • n. Either of the two haploid nuclei (of a sperm and ovum) that fuse during fertilization

from the GNU version of the Collaborative International Dictionary of English

  • n. One of the two bodies or nuclei (called male and female pronuclei) which unite to form the first segmentation nucleus of an impregnated ovum.

from The Century Dictionary and Cyclopedia

  • n. A primitive nucleus; the nucleus of an ovum or of a spermatozoön before these have united to form the definitive nucleus of an impregnated ovum.
  • n. In botany, the nucleus of a conjugating gamete, which on coalescing with another pronucleus forms the germ-nucleus.

from WordNet 3.0 Copyright 2006 by Princeton University. All rights reserved.

  • n. the nucleus of the ovum or sperm after fertilization but before they fuse to form the nucleus of the zygote


Sorry, no etymologies found.


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  • "Having pierced the yolk, the spermatozoön loses its tail, while its head and connecting piece assume the form of a nucleus containing a cluster of chromosomes. This constitutes the male pronucleus, and associated with it there are a centriole and centrosome."
    - Henry Gray, 'Anatomy of the Human Body', 1918.

    September 20, 2009