obtuse, dense, slow-witted, blunt
Oui, on peut dire ça, mais on sait que c'était un instrument obtus.
Yes, you could say that, but we know it was a blunt instrument.
— Mother (2009)
Où sont les miens, les obtus, ceux des origines ?
Where are mine—the obtuse ones, those from the beginning?
— Les Ailes du désir (1987)
Tu es si obtus en ce moment.
You're being so obtuse right now.
— Paddington 2 (2017)
Jules, t'es obtus ou quoi ?
Jules, are you being dense or what?
— Diva (1981)