Stupefactive refers to something that causes drowsiness or dullness, and antonyms represent words that have opposite or contrasting meanings. The antonyms for stupefactive include terms such as energizing, stimulating, invigorating, and awakening. The opposite of something that dulls the senses, stupefactive's antonyms are words that lift the spirits, wake up the mind and increase alertness. Some examples of useful antonyms for stupefactive might include words like active, lively, vibrant, and enlivening. Antonyms provide a useful tool for expanding your vocabulary and expressing your ideas with greater precision and clarity.