thickheaded, obtuse, stupid...

blockhead, dunce, dimwit...

thickheaded, insensitive, dull...

blunt (e.g. sword), dull, lazy...

becoming dull, slowing down

to become blunt, to grow dull, to become less capable...

blunt weapon

to blunt, to dull, to weaken

local train, slow train

blunt (e.g. sword), dull, lazy...

slow

to anneal

obtuse angle

thickheaded, slow-witted, phlegmatic...

dull pain

becoming numb, becoming desensitized

silk damask, satin damask

stupidity, dull person, dullness

dull or blunt sword

dark gray, dark grey, donjiki (clerical dress)

slow-footed

blockhead, a fool

slow-witted

dullard (gen. from not picking up on other people's feelings)

dullard (gen. from not picking up on other people's feelings)

dark sleeper (species of sleeper goby, Odontobutis obscura)

obtuse (of the shape of a leaf), rounded

becoming dull (of a knife, one's wits, etc.)...

to become dim-witted, to lose one's edge, to become insensitive

slowly, sluggishly