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

abstract data type
ADT

    (ADT) A kind of data abstraction where a
   type's internal form is hidden behind a set of access
   functions.  Values of the type are created and inspected only
   by calls to the access functions.  This allows the
   implementation of the type to be changed without requiring any
   changes outside the module in which it is defined.

   Objects and ADTs are both forms of data abstraction, but
   objects are not ADTs.  Objects use procedural abstraction
   (methods), not type abstraction.

   A classic example of an ADT is a stack data type for which
   functions might be provided to create an empty stack, to
   push values onto a stack and to pop values from a stack.

   Reynolds paper
   (http://cis.upenn.edu/~gunter/publications/documents/taoop94.html).

   Cook paper "OOP vs ADTs"
   (http://wcook.org/papers/OOPvsADT/CookOOPvsADT90.pdf).

   (2003-07-03)