The Collaborative International Dictionary of English v.0.48:

Ponder \Pon"der\, v. t. [imp. & p. p. Pondered; p. pr. & vb.
   n. Pondering.] [L. ponderare, fr. pondus, ponderis, a
   weight, fr. pendere to weigh: cf. F. pond['e]rer. See
   Pendant, and cf. Pound a weight.]
   [1913 Webster]
   1. To weigh. [Obs.]
      [1913 Webster]

   2. To weigh in the mind; to view with deliberation; to
      examine carefully; to consider attentively.
      [1913 Webster]

            Ponder the path of thy feet.          --Prov. iv.
                                                  26.
      [1913 Webster]

   Syn: To Ponder, Consider, Muse.

   Usage: To consider means to view or contemplate with fixed
          thought. To ponder is to dwell upon with long and
          anxious attention, with a view to some practical
          result or decision. To muse is simply to think upon
          continuously with no definite object, or for the
          pleasure it gives. We consider any subject which is
          fairly brought before us; we ponder a concern
          involving great interests; we muse on the events of
          childhood.
          [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Ponder \Pon"der\, v. i.
   To think; to deliberate; to muse; -- usually followed by on
   or over. --Longfellow.
   [1913 Webster]

WordNet (r) 3.0 (2006):

ponder
    v 1: reflect deeply on a subject; "I mulled over the events of
         the afternoon"; "philosophers have speculated on the
         question of God for thousands of years"; "The scientist
         must stop to observe and start to excogitate" [syn: chew
         over, think over, meditate, ponder, excogitate,
         contemplate, muse, reflect, mull, mull over,
         ruminate, speculate]

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

Ponder

   A non-strict polymorphic, functional language by Jon
   Fairbairn .

   Ponder's type system is unusual.  It is more powerful than the
   Hindley-Milner type system used by ML and Miranda and
   extended by Haskell.  Ponder adds extra recursive 'mu' types
   to those of Girard's System F, allowing more general
   recursion.  Surprisingly, the type system and type
   inference algorithm are still not completely understood.

   ["Ponder and its Type System", J. Fairbairn, TR 31, Cambridge
   U Computer Lab, Nov 1982].

   [J. Fairbairn, "Design and Implementation of a Simple Typed
   Language based on the Lambda-Calculus", Technical Report
   No. 75, Computer Laboratory, University of Cambridge, May
   1985].

   [J. Fairbairn, "A New Type-Checker for a Functional Language",
   Technical Report No. 53, Computer Laboratory, University of
   Cambridge, 1984].

   [J. Fairbairn, "Some Types with Inclusion Properties in
   \forall, \rightarrow, \mu", Technical Report No. 171, Computer
   Laboratory, University of Cambridge, Jun 1989].

   [Valeria C. V. de Paiva, "Subtyping in Ponder (Preliminary
   Report)", Technical Report No. 203, Computer Laboratory,
   University of Cambridge, Aug 1990].