The term GROOM FASTIDIOUSLY can be summarized by the crossword solution PREEN, which is a five-letter word. To PREEN means to groom oneself carefully and meticulously, often with the use of a comb or brush. This term is commonly used in reference to birds, who use their beaks to clean and arrange their feathers. In a figurative sense, it can also refer to people who take great care in their appearance.