The Collaborative International Dictionary of English v.0.48:
doctor \doc"tor\, n. [OF. doctur, L. doctor, teacher, fr. docere
to teach. See Docile.]
1. A teacher; one skilled in a profession, or branch of
knowledge; a learned man. [Obs.]
One of the doctors of Italy, Nicholas Macciavel. --
2. An academical title, originally meaning a man so well
versed in his department as to be qualified to teach it.
Hence: One who has taken the highest degree conferred by a
university or college, or has received a diploma of the
highest degree; as, a doctor of divinity, of law, of
medicine, of music, or of philosophy. Such diplomas may
confer an honorary title only.
3. One duly licensed to practice medicine; a member of the
medical profession; a physician.
By medicine life may be prolonged, yet death
Will seize the doctor too. -- Shak.
4. Any mechanical contrivance intended to remedy a difficulty
or serve some purpose in an exigency; as, the doctor of a
calico-printing machine, which is a knife to remove
superfluous coloring matter; the doctor, or auxiliary
engine, called also donkey engine.
5. (Zool.) The friar skate. [Prov. Eng.]
Doctors' Commons. See under Commons.
Doctor's stuff, physic, medicine. --G. Eliot.
Doctor fish (Zool.), any fish of the genus Acanthurus;
the surgeon fish; -- so called from a sharp lancetlike
spine on each side of the tail. Also called barber fish.
See Surgeon fish.