LETHARGY Meaning of LETHARGY in English leth ‧ ar ‧ gy /ˈleθədʒi $ -ər-/ BrE AmE noun [uncountable] the feeling of being lethargic:New mothers often complain of lethargy and mild depression. Longman Dictionary of Contemporary English. Longman - Словарь современного английского языка. 2012