sul ‧ len /ˈsʌlən/ BrE AmE adjective
[ Date: 1300-1400 ; Origin: Probably from an unrecorded Anglo-French solein 'single, solitary, sullen' , from Latin solus 'alone' ]
1 . angry and silent, especially because you feel life has been unfair to you ⇨ morose :
Bill sat in sullen silence and refused to eat his lunch.
a look of sullen resentment
2 . literary a sullen sky or sea is dark and looks as if bad weather is coming SYN overcast
—sullenly adverb
—sullenness noun [uncountable]