Something that occupies space and can be perceived by one or more senses; a physical body, a physical substance, or the universe as a whole. Physics Something that has mass and exists as a solid, liquid, gas, or plasma. A specific type of substance: inorganic matter. Discharge or waste, such as pus or feces, from a living organism. Philosophy In Aristotelian and Scholastic use, that which is in itself undifferentiated and formless and which, as the subject of change and development, receives form and becomes substance. The substance of thought or expression as opposed to the manner in which it is stated or conveyed. A subject of concern, feeling, or action: matters of foreign policy; a personal matter. See Synonyms at subject. Trouble or difficulty: What's the matter with your car? An approximated quantity, amount, or extent: The construction will last a matter of years. Something printed or otherwise set down in writing: reading matter. Something sent by mail. Printing Composed type. Printing Material to be set in type. To be of importance: "Love is most nearly itself/When here and now cease to matter\u201d ( T.S. Eliot). See Synonyms at count1. as a matter of fact In fact; actually. for that matter So far as that is concerned; as for that. no matter Regardless of: "Yet there isn't a train I wouldn't take,/No matter where it's going\u201d ( Edna St. Vincent Millay).