Flue/fluː/ Definition 1 of 3Pro Tip 1/3Part of Home Flue usually refers to a part of a house where fire or heat is involved. Remember to clean the flue before lighting the fireplace. Pro Tip 2/3Safety Concern A blocked or damaged flue can be dangerous, as it can cause gases to enter the home. They had to evacuate the house when the flue got blocked. Pro Tip 3/3Not Always Visible Flues are often hidden within walls or chimneys and not openly visible. The inspector checked the integrity of the hidden flue.