curiosus

Back-formation from incūriōsus (“careless, negligent”) by deletion of the negative prefix in- (“un-”) in order to remain with the opposite meaning.

• (Classical Latin) IPA^(key): /kuː.riˈoː.sus/, [kuːriˈoːs̠ʊs̠]
• (modern Italianate Ecclesiastical) IPA^(key): /ku.riˈo.sus/, [kuriˈɔːs̬us]

cūriōsus (feminine cūriōsa, neuter cūriōsum, comparative cūriōsior); first/second-declension adjective

1. Careful, diligent, thoughtful, devoted.
2. Elaborate, complicated.
3. That injures himself by care; careworn, emaciated, wasted, lean.
4. (in a good sense) Curious, inquisitive.
5. (in a bad sense) Meddlesome, officious, prying, interfering, curious, inquisitive.
   • 1st c. BC, Marcus Tullius Cicero, De Finibus Bonorum et Malorum :

     Etenim si delectamur cum scribimus, quis est tam invidus qui ab eo nos abducat? [...] Sic isti curiosi, quos offendit noster minime nobis iniucundus labor.

     Indeed if I enjoy writing, who would be so spiteful as to keep me from it? [...] Thus are these meddlesome individuals to whom this my not at all unpleasant (to me) endeavor is offensive.

First/second-declension adjective.

• cūriōsē
• cūriōsitās
• cūriōsulus
• incūriōsus

cūriōsus m (genitive cūriōsī); second declension

1. One who pries; a spy or scout; secret police, informer.

Second-declension noun.

• “curiosus”, in Charlton T. Lewis and Charles Short (1879) A Latin Dictionary, Oxford: Clarendon Press
• curiosus in Charles du Fresne du Cange’s Glossarium Mediæ et Infimæ Latinitatis (augmented edition with additions by D. P. Carpenterius, Adelungius and others, edited by Léopold Favre, 1883–1887)
• curiosus in Gaffiot, Félix (1934) Dictionnaire illustré latin-français, Hachette.