The Collaborative International Dictionary of English v.0.48:

Divisor \Di*vi"sor\, n. [L., fr. dividere. See Divide.]
   (Math.)
   The number by which the dividend is divided.
   [1913 Webster]

   Common divisor. (Math.) See under Common, a.
      [1913 Webster]

WordNet (r) 3.0 (2006):

divisor
    n 1: one of two or more integers that can be exactly divided
         into another integer; "what are the 4 factors of 6?" [syn:
         divisor, factor]
    2: the number by which a dividend is divided

The Free On-line Dictionary of Computing (30 December 2018):

divisor

   A quantity that evenly divides another quantity.

   Unless otherwise stated, use of this term implies that the
   quantities involved are integers.  (For non-integers, the more
   general term factor may be more appropriate.)

    Example: 3 is a divisor of 15.
    Example: 3 is not a divisor of 14.

   (1997-03-07)