Meanings

blockhead

obtuse triangle

slow-footed

dull or blunt sword

slow-witted

dark gray

sharp or blunt

dull-witted

to become less capable

to waver in one's resolution

to blunt

dull yellow

dull sound

blunt (e.g. sword)

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)

dim-witted

jet black

grey tinged with green