lusus naturae

From Latin lūsus nātūrae (“sport of Nature”),[1] from lūsus (“playing”, “sport”)[1] + nātūrae (“of Nature”), genitive singular of nātūra (“Nature”). Plural from Latin lūsūs nātūræ (“sports of Nature”), from lūsūs (“playings”, “sports”).

singular

• (Received Pronunciation) enPR: lo͞oʹsəs nətyo͝oəʹrē, lyo͞oʹsəs nətyo͝oəʹrē, IPA^(key): /ˈluːsəs nəˈtjʊəɹiː/,[1] /ˈljuːsəs nəˈtjʊəɹiː/,[1]

plural

• (Received Pronunciation) enPR: lo͞oʹso͞os nətyo͝oəʹrē, lyo͞oʹso͞os nətyo͝oəʹrē, IPA^(key): /ˈluːsuːs nəˈtjʊəɹiː/, /ˈljuːsuːs nəˈtjʊəɹiː/

lusus naturae (plural lusus naturae)

1. (historical, originally) A sportive quality in Nature to which abnormal forms were formerly ascribed; a supposed capricious act of Nature regarded as the cause and origin of anomalies in a given organism.
   • 1665, Robert Hooke, Micrographia, section XXII:

     I have observ'd some meshes to have 5, 6, 7, 8, or 9. sides, and some to have onely one, so exceeding various is the Lusus Naturæ in this body.

2. (countable) An organism exhibiting marked such deviation from the norm, seeming to be the result of sportive design; a freak of nature.

• lusus naturæ (rare, archaic, singular and plural)
• lusûs naturæ (rare, nonstandard, archaic, plural only)

• (capricious act of Nature): God's joke
• (variant of seemingly sportive design): freak of nature; lusus (dated, 19 the century)[1]

lūsus nātūrae m (genitive lūsūs nātūrae); fourth declension

1. a deformed or strangely marked creature; a freak

Fourth-declension noun with an indeclinable portion.