The Collaborative International Dictionary of English v.0.48:

pearly everlasting \pearly everlasting\ n. (Bot.)
   an American everlasting (Anaphalis margaritacea) having
   foliage with soft wooly hairs and corymbose heads with
   pearly-white scarious involucres.

   Syn: cottonweed, Anaphalis margaritacea.
        [WordNet 1.5 +MW10]

The Collaborative International Dictionary of English v.0.48:

Everlasting \Ev`er*last"ing\, n.
   1. Eternal duration, past or future; eternity.
      [1913 Webster]

            From everlasting to everlasting, thou art God. --Ps.
                                                  xc. 2.
      [1913 Webster]

   2. (With the definite article) The Eternal Being; God.
      [1913 Webster]

   3. (Bot.) A plant whose flowers may be dried without losing
      their form or color, as, the pearly everlasting
      (Anaphalis margaritacea), the immortelle (Xeranthemum
      anuum) of the French, the cudweeds, etc.
      [1913 Webster]

   4. A cloth fabric for shoes, etc. See Lasting.
      [1913 Webster]

WordNet (r) 3.0 (2006):

Anaphalis margaritacea
    n 1: an American everlasting having foliage with soft wooly
         hairs and corymbose heads with pearly white bracts [syn:
         pearly everlasting, cottonweed, Anaphalis
         margaritacea]