adjective

1. halfway between two given points, times, limits, etc.; also, equally distant from all sides or extremities; in the center; mean
2. in between; intermediate; intervening
3. Gram.
   1. denoting the voice or form of a verb whose subject is represented as acting reflexively, or upon itself: in Greek, such verbs are usually passive in grammatical form
   2. in or of the middle voice
4. Geol. designating a division of a period or a formation between those called Upper and Lower
5. designating a stage in language development intermediate between those called Old and Modern Middle English

Etymology: ME middel < OE < midd-, mid + -el, -le

noun

1. a point or part halfway between extremes; middle point, part, time, etc.
2. something intermediate
3. the middle part of the body; waist
4. Gram. the middle voice
5. middle term

transitive verb, intransitive verb middled -·dled, middling -·dling