The Collaborative International Dictionary of English v.0.48:

Pupil \Pu"pil\, n. [F. pupille, n. fem., L. pupilla the pupil of
   the eye, originally dim. of pupa a girl. See Puppet, and
   cf. Pupil a scholar.] (Anat.)
   The aperture in the iris; the sight, apple, or black of the
   eye. See the Note under Eye, and Iris.
   [1913 Webster]

   Pin-hole pupil (Med.), the pupil of the eye when so
      contracted (as it sometimes is in typhus, or opium
      poisoning) as to resemble a pin hole. --Dunglison.
      [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Pupil \Pu"pil\, n. [F. pupille, n. masc. & fem., L. pupillus,
   pupilla, dim. of pupus boy, pupa girl. See Puppet, and cf.
   Pupil of the eye.]
   1. A youth or scholar of either sex under the care of an
      instructor or tutor.
      [1913 Webster]

            Too far in years to be a pupil now.   --Shak.
      [1913 Webster]

            Tutors should behave reverently before their pupils.
                                                  --L'Estrange.
      [1913 Webster]

   2. A person under a guardian; a ward. --Dryden.
      [1913 Webster]

   3. (Civil Law) A boy or a girl under the age of puberty, that
      is, under fourteen if a male, and under twelve if a
      female.
      [1913 Webster]

   Syn: Learner; disciple; tyro. -- See Scholar.
        [1913 Webster]

WordNet (r) 3.0 (2006):

pupil
    n 1: a learner who is enrolled in an educational institution
         [syn: student, pupil, educatee]
    2: the contractile aperture in the center of the iris of the
       eye; resembles a large black dot
    3: a young person attending school (up through senior high
       school) [syn: schoolchild, school-age child, pupil]