Hebetation is a word that refers to a state of mental lethargy or dullness. Synonyms for this word include sluggishness, torpor, somnolence, stupor, and lethargy. These words all describe a lack of mental sharpness or alertness, and can be used interchangeably with hebetation in most contexts. Other synonyms for hebetation might include apathy, listlessness, and inertia, as these words also describe a general sense of disinterest or lack of motivation. When you're trying to convey a sense of mental sluggishness or dullness, any of these synonyms can be used to help you get your point across.