dull-witted russian

• тупо́й

  stupid (dull, slow-witted), apathetic

  blunt / obtuse

• непоня́тливый

  slow-witted, dull

• твердоло́бый

  thick-headed, chuckle-headed, thick-skulled, dull-witted, die-hard

• затормо́женный

  inhibited, sluggish, slow-witted, dull

• торможённый

  slow-witted, inhibited, dull, sluggish, slow on the uptake

• тормозну́вший

  slow-witted, dull, stupid, dense

• тупи́вший

  slow-witted, dull-witted, having been stuck/confused

• тупя́щий

  blunting, dulling

  slow-witted, dull-witted, acting stupidly (colloquial)