Synset

slow to learn or understand; lacking intellectual acuity
<adj.all>   freq. cnt.: 11 freq. cnt.: 9 freq. cnt.: 1 freq. cnt.: 1

dense

dim

dull

dumb

obtuse

slow

sample sentences

"so dense he never understands anything I say to him"
"never met anyone quite so dim"
"although dull at classical learning, at mathematics he was uncommonly quick"- Thackeray
"dumb officials make some really dumb decisions"
"he was either normally stupid or being deliberately obtuse"
"worked with the slow students"