| Term | Definition |
| malevolent | having bad feelings toward someone or something; spite, hatred |
| malapropism | a word used in the wrong way, usually with humorous results |
| malicious | desiring to harm someone or something |
| malodorous | bad-smelling |
| malady | a bad health condition; a disease |
| malaria | illness believed to be spread by bad air, actually spread by mosquitoes |
| malediction | bad speech, a curse |
| malefactor | one who does wrong; a villain |
| malignant | bad or harmful; producing death |
| malpractice | performing one's duty in a bad or wrong way |