The term 'FEEL GRIEF' can be summarized by the crossword solution 'MOURN, ' which is a five-letter word. To MOURN is to feel grief or sorrow for someone or something, usually due to a death or loss. It is an expression of deep sadness and can involve outward expressions such as crying or wearing black clothing. Mourning is a common response to death and is often done in a communal setting with friends and family.