The Collaborative International Dictionary of English v.0.48:

1 \1\ adj.
   1. used of a single unit or thing; not two or more; --
      representing the number one as an Arabic numeral.

   Syn: one, i, ane
        [WordNet 1.5 +PJC]

WordNet (r) 3.0 (2006):

1
    adj 1: used of a single unit or thing; not two or more; "`ane'
           is Scottish" [syn: one, 1, i, ane]
    n 1: the smallest whole number or a numeral representing this
         number; "he has the one but will need a two and three to go
         with it"; "they had lunch at one" [syn: one, 1, I,
         ace, single, unity]

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

one
1

    The lowest positive integer and the basis for
   counting.  Multiplication by one is an identity operator and,
   since one is its own reciprocal, so is division by one.  One is
   the result of dividing any non-zero number by itself.  One raised
   to any power is one and raising to the power one is also an
   identity operator.

    The largest digit in binary, related to the value true
   in Boolean algebra.  Digital computers typically represent one
   by a high voltage and zero by a low voltage.

   (2012-12-31)