Answer: The connotation of the word "smell" in the sentence provided is "stench".
Explanation: The word "smell" has a negative connotation in the sentence provided since "grimaced", which is also part of the sentence, has a negative connotation too. "Grimaced" means to make a facial expression that shows disgust. In that way, taking into account the context of the sentence, the word "smell" has been used to refer to a stench, that is to say to a very unpleasant smell.