Baretti: A dictionary of the English and Italian languages
Ottús-o, adj.
1. (geom. t.) obtuse, not acute. Angolo —, an obtuse angle, an angle which contains more than ninety degrees; 2. obtuse, blunt; 3. (fig.) dull of apprehension. Cervello —, a dull brain. Uomo —, a dull, heavy man. Sapore —, an insipid, flat flavour;adv. Ottús-aménte.
Florio: a worlde of wordes, or most copious, dictionarie in Italian and English
ottuso: dull, blunt, heauie, leaden-witted, sluggish, without spirit. Also in Mathematikes it is the propertie of an angle that is bigger then a right angle.