sull
/sʌl/verb
no obj.
1- US informal dialect (of an animal) refuse to advance〈美, 非正式, 方〉（动物）拒绝前进。
1.1
- (of a person) become sullen; sulk（人）变得忧郁, 生（闷）气; 愠怒：
don't sull up on me, let's get it aired.
不要对我生闷气了, 让我们说出来吧。
词源
mid 19th cent.: back-formation from SULLEN.