The word "stupefier" is defined as something that causes a state of unconsciousness or a loss of mental acuity. There are several synonyms for this word that can be used to describe similar effects. For instance, terms like "sedative," "tranquilizer," "narcotic," and "anesthetic" can all be used to describe substances that have a stupefying effect on the body and mind. Alternatively, phrases like "brain fog," "mental haze," and "state of confusion" can be used to describe the subjective experience of being stupefied. Regardless of how you choose to describe it, the sensation of being stupefied is one that can be unsettling and even dangerous, so it's important to avoid situations where this might occur.