| Term | Definition |
| louse | A small insect parasitic on and sucking the blood of mammals. |
| lovable | Amiable. |
| low-spirited | Despondent. |
| lowly | Rudely. |
| lucid | Mentally sound. |
| lucrative | Highly profitable. |
| ludicrous | Laughable. |
| luminary | One of the heavenly bodies as a source of light. |
| luminescent | Showing increase of light. |
| luminescence | Showing increase. |
| luminosity | The quality of giving or radiating light. |
| luminous | Giving or radiating light. |
| lunacy | Mental unsoundness. |
| lunar | Pertaining to the moon. |
| lunatic | An insane person. |
| lune | The moon. |
| lurid | Ghastly and sensational. |
| luscious | Rich, sweet, and delicious. |
| lustrous | Shining. |
| luxuriance | Excessive or superfluous growth or quantity. |
| luxuriant | Abundant or superabundant in growth. |
| luxuriate | To live sumptuously. |
| lying | Untruthfulness. |
| lyre | One of the most ancient of stringed instruments of the harp class. |
| lyric | Fitted for expression in song. |
| macadamize | To cover or pave, as a path or roadway, with small broken stone. |
| machinery | The parts of a machine or engine, taken collectively. |
| machinist | One who makes or repairs machines, or uses metal-working tools. |
| macrocosm | The whole of any sphere or department of nature or knowledge to which man is related. |
| madden | To inflame with passion. |
| Madonna | A painted or sculptured representation of the Virgin, usually with the infant Jesus. |
| magician | A sorcerer. |
| magisterial | Having an air of authority. |
| magistracy | The office or dignity of a magistrate. |
| magnanimous | Generous in treating or judging others. |
| magnate | A person of rank or importance. |
| magnet | A body possessing that peculiar form of polarity found in nature in the lodestone. |
| magnetize | To make a magnet of, permanently, or temporarily. |
| magnificence | The exhibition of greatness of action, character, intellect, wealth, or power. |
| magnificent | Grand or majestic in appearance, quality, or action. |
| magnitude | Importance. |
| maharaja | A great Hindu prince. |
| maidenhood | Virginity. |
| maintain | To hold or preserve in any particular state or condition. |
| maintenance | That which supports or sustains. |
| maize | Indian corn: usually in the United States called simply corn. |
| makeup | The arrangements or combination of the parts of which anything is composed. |
| malady | Any physical disease or disorder, especially a chronic or deep-seated one. |
| malaria | A fever characterized by alternating chills, fever, and sweating. |
| malcontent | One who is dissatisfied with the existing state of affairs. |