若存若亡

Explanation: Sometimes in mind, and sometimes forgotten. Used to describe the Ruoyouruowu, elusive. 　　Usage: Joint type; as predicate, attributive, adverbial; that elusive 　　Source: Qin Li Er, "I": "Sergeant Wen Road, ground and the line of; sergeant told about the Tao, if the deposit if the dead; Corporal Tao and laughter." Thesaurus:  Ruoyouruowu, partly hidden and partly visible, loom