LATIN DICTIONARYLexicon Latīnum
adverb

in nuce

in nuce (not comparable)
Classical[ˈɪn ˈnʊ.kɛ]Ecclesiastical[ˈin ˈnuː.t͡ʃe]

Meaning

  1. New Latinnot comparablein a nutshell; briefly stated
    […] adeoque sola eruendas ratione, in nuce, quod dicitur, aut velut in tabula depictas, simul exhibeam.[…] let me present, at the same time, those things that are to be unearthed by reason alone, in a nutshell, as it is said, or as if depicted in an image.1731, Jakob Wilde, Sueciæ Historia Pragmatica Quæ vulgò Jus Publicum dicitur […], page 5:
  2. New Latinnot comparablein the embryonic phase; said of something which is just developing or being developed

Origins

From in + nuce, the ablative singular of nux (“nut”): literally, “in a nut”. Derived from an anecdote in Pliny the Elder, who ascribes to Cicero the claim that the whole Iliad was once written on parchment and enclosed within a nutshell (Naturalis Historia 7.21.85).

Quick answers

What does in nuce mean in Latin?
in nuce, a adverb, means “in a nutshell; briefly stated; in the embryonic phase”.
How do you pronounce in nuce?
In classical Latin, [ˈɪn ˈnʊ.kɛ]; in ecclesiastical (church) Latin, [ˈin ˈnuː.t͡ʃe].