any ringing or buzzing in the ear not resulting from an external stimulus
See tinnitus in American Heritage Dictionary 4
(tĭ-nīˈtəs, tĭnˈĭ-)
nounpl.tin·ni·tus·es
A sound in one ear or both ears, such as buzzing, ringing, or whistling, occurring without an external stimulus and usually caused by a specific condition, such as an ear infection, the use of certain drugs, a blocked auditory tube or canal, or a head injury.