Lassitude: Weakness, weariness, listlessness, exhaustion, lethargy. For example, the patient complained of lassitude. From Latin lassitudo, from lassus meaning weary. From Healthy Resources 10 Rheumatoid Arthritis Symptoms How IL Inhibitors Work to Treat PsoriasisModerate to Severe UC: Targeted Solutions Featured Centers What Are the Best PsA Treatments for You?Understanding Biologics 10 Things People With Depression Wish You Knew