Soporifousness is a relatively obscure word that denotes the quality of inducing sleep or drowsiness. Some synonyms for soporifousness include somnolence, slumberousness, drowsiness, lethargy, and sleepiness. These words all describe a state of being mentally and physically sluggish and lacking in energy. Other possible alternatives for soporifousness include torpor, lassitude, fatigue, and hebetude, which all suggest a feeling of dullness or numbness. Additionally, some other words that might be associated with soporifousness include dullness, monotony, and ennui, which suggest a feeling of boredom or lack of stimulation. Overall, soporifousness and its synonyms describe a state of sleepiness and sluggishness that can be caused by a variety of factors.