n.1. the act or process of causing something (e.g., a disease) to pass from one place or person to another. See also horizontal transmission. 2. in neuroscience, see neurotransmission. 3. the inheritance of traits through successive generations. 4. the handing down of customs and mores from generation to generation. See social transmission. See also cultural heritage. —transmissibleadj.—transmitvb.