The Collaborative International Dictionary of English v.0.48:

Pyramidal \Py*ram`i*dal\, a. [Cf. F. pyramidal.]
   [1913 Webster]
   1. Of or pertaining to a pyramid; in the form of a a pyramid;
      pyramidical; as, pyramidal cleavage.
      [1913 Webster]

            The mystic obelisks stand up
            Triangular, pyramidal.                --Mrs.
                                                  Browning.
      [1913 Webster]

   2. (Crystallog.) Same as Tetragonal.
      [1913 Webster]

   Pyramidal numbers (Math.), certain series of figurate
      numbers expressing the number of balls or points that may
      be arranged in the form of pyramids. Thus 1, 4, 10, 20,
      35, etc., are triangular pyramidal numbers; and 1, 5, 14,
      30, 55, etc., are square pyramidal numbers.
      [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Pyramidal \Py*ram"i*dal\, n. (Anat.)
   One of the carpal bones. See Cuneiform, n., 2
   (b) .
       [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Cuneiform \Cu*ne"i*form\, Cuniform \Cu"ni*form\, n.
   1. The wedge-shaped characters used in ancient Persian and
      Assyrian inscriptions. --I. Taylor (The Alphabet).
      [1913 Webster]

   2. (Anat.)
      (a) One of the three tarsal bones supporting the first,
          second third metatarsals. They are usually designated
          as external, middle, and internal, or ectocuniform,
          mesocuniform, and entocuniform, respectively.
      (b) One of the carpal bones usually articulating with the
          ulna; -- called also pyramidal and ulnare.
          [1913 Webster]

WordNet (r) 3.0 (2006):

pyramidal
    adj 1: resembling a pyramid [syn: pyramidal, pyramidic,
           pyramidical]