The Collaborative International Dictionary of English v.0.48:

Heap \Heap\ (h[=e]p), n. [OE. heep, heap, heap, multitude, AS.
   he['a]p; akin to OS. h[=o]p, D. hoop, OHG. houf, h[=u]fo, G.
   haufe, haufen, Sw. hop, Dan. hob, Icel. h[=o]pr troop, flock,
   Russ. kupa heap, crowd, Lith. kaupas. Cf. Hope, in Forlorn
   hope.]
   1. A crowd; a throng; a multitude or great number of persons.
      [Now Low or Humorous]
      [1913 Webster]

            The wisdom of a heap of learned men.  --Chaucer.
      [1913 Webster]

            A heap of vassals and slaves.         --Bacon.
      [1913 Webster]

            He had heaps of friends.              --W. Black.
      [1913 Webster]

   2. A great number or large quantity of things not placed in a
      pile; as, a heap of trouble. [Now Low or Humorous]
      [1913 Webster]

            A vast heap, both of places of scripture and
            quotations.                           --Bp. Burnet.
      [1913 Webster]

            I have noticed a heap of things in my life. --R. L.
                                                  Stevenson.
      [1913 Webster]

   3. A pile or mass; a collection of things laid in a body, or
      thrown together so as to form an elevation; as, a heap of
      earth or stones.
      [1913 Webster]

            Huge heaps of slain around the body rise. --Dryden.
      [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Heap \Heap\, v. t. [imp. & p. p. Heaped (h[=e]pt); p. pr. &
   vb. n. Heaping.] [AS. he['a]pian.]
   1. To collect in great quantity; to amass; to lay up; to
      accumulate; -- usually with up; as, to heap up treasures.
      [1913 Webster]

            Though he heap up silver as the dust. --Job. xxvii.
                                                  16.
      [1913 Webster]

   2. To throw or lay in a heap; to make a heap of; to pile; as,
      to heap stones; -- often with up; as, to heap up earth; or
      with on; as, to heap on wood or coal.
      [1913 Webster]

   3. To form or round into a heap, as in measuring; to fill (a
      measure) more than even full.
      [1913 Webster]

WordNet (r) 3.0 (2006):

heap
    n 1: a collection of objects laid on top of each other [syn:
         pile, heap, mound, agglomerate, cumulation,
         cumulus]
    2: (often followed by `of') a large number or amount or extent;
       "a batch of letters"; "a deal of trouble"; "a lot of money";
       "he made a mint on the stock market"; "see the rest of the
       winners in our huge passel of photos"; "it must have cost
       plenty"; "a slew of journalists"; "a wad of money" [syn:
       batch, deal, flock, good deal, great deal,
       hatful, heap, lot, mass, mess, mickle, mint,
       mountain, muckle, passel, peck, pile, plenty,
       pot, quite a little, raft, sight, slew, spate,
       stack, tidy sum, wad]
    3: a car that is old and unreliable; "the fenders had fallen off
       that old bus" [syn: bus, jalopy, heap]
    v 1: bestow in large quantities; "He heaped him with work"; "She
         heaped scorn upon him"
    2: arrange in stacks; "heap firewood around the fireplace";
       "stack your books up on the shelves" [syn: stack, pile,
       heap]
    3: fill to overflow; "heap the platter with potatoes"

The Free On-line Dictionary of Computing (19 January 2023):

heap

   1.  An area of memory used for dynamic memory
   allocation where blocks of memory are allocated and freed in
   an arbitrary order and the pattern of allocation and size of
   blocks is not known until run time.  Typically, a program
   has one heap which it may use for several different purposes.

   Heap is required by languages in which functions can return
   arbitrary data structures or functions with free variables
   (see closure).  In C functions malloc and free provide
   access to the heap.

   Contrast stack.  See also dangling pointer.

   2.  A data structure with its elements partially
   ordered (sorted) such that finding either the minimum or the
   maximum (but not both) of the elements is computationally
   inexpensive (independent of the number of elements), while
   both adding a new item and finding each subsequent
   smallest/largest element can be done in O(log n) time, where n
   is the number of elements.

   Formally, a heap is a binary tree with a key in each node,
   such that all the leaves of the tree are on two adjacent
   levels; all leaves on the lowest level occur to the left and
   all levels, except possibly the lowest, are filled; and the
   key in the root is at least as large as the keys in its
   children (if any), and the left and right subtrees (if they
   exist) are again heaps.

   Note that the last condition assumes that the goal is finding
   the minimum quickly.

   Heaps are often implemented as one-dimensional arrays.
   Still assuming that the goal is finding the minimum quickly
   the invariant is

      heap[i] <= heap[2*i] and heap[i] <= heap[2*i+1] for all i,

   where heap[i] denotes the i-th element, heap[1] being the
   first.  Heaps can be used to implement priority queues or in
   sort algorithms.

   (1996-02-26)