lack of energy synonym
; lack of energy : she was overcome by lassitude and retired to bed | a patient complaining of lassitude and inability to concentrate. prolonged periods of lassitude lethargy, listlessness, weariness, languor, sluggishness, tiredness, fatigue, torpor, lifelessness, apathy. antonym vigor.
lethargy - inactivity; showing an unusual lack of energy; the general appearance of sluggishness alarmed his friends languor, phlegm, sluggishness, flatness inertia, inactiveness, inactivity - a disposition to remain inactive or inert; he had to overcome his inertia and get back to work