The Collaborative International Dictionary of English v.0.48:

Myrrh \Myrrh\, n. [OE. mirre, OF. mirre, F. myrrhe, L. myrrha,
   murra, Gr. ?; cf. Ar. murr bitter, also myrrh, Heb. mar
   bitter.]
   A gum resin, usually of a yellowish brown or amber color, of
   an aromatic odor, and a bitter, slightly pungent taste. It is
   valued for its odor and for its medicinal properties. It
   exudes from the bark of a shrub of Abyssinia and Arabia, the
   Commiphora Myrrha (syn. Balsamodendron Myrrha) of the
   family Burseraceae, or from the Commiphora abyssinica.
   The myrrh of the Bible is supposed to have been partly the
   gum above named, and partly the exudation of species of
   Cistus, or rockrose.
   [1913 Webster]

   False myrrh. See the Note under Bdellium.
      [1913 Webster]

WordNet (r) 3.0 (2006):

myrrh
    n 1: aromatic resin that is burned as incense and used in
         perfume [syn: myrrh, gum myrrh, sweet cicely]

Moby Thesaurus II by Grady Ward, 1.0:

29 Moby Thesaurus words for "myrrh":
   ambergris, ambrosia, aromatic, aromatic gum, aromatic water, attar,
   attar of roses, balm, balm of Gilead, balsam, bay oil,
   bergamot oil, champaca oil, civet, essence, essential oil, extract,
   fixative, heliotrope, jasmine oil, lavender oil, musk, myrcia oil,
   parfum, perfume, perfumery, rose oil, scent, volatile oil



Easton's 1897 Bible Dictionary:

Myrrh
   Heb. mor. (1.) First mentioned as a principal ingredient in the
   holy anointing oil (Ex. 30:23). It formed part of the gifts
   brought by the wise men from the east, who came to worship the
   infant Jesus (Matt. 2:11). It was used in embalming (John
   19:39), also as a perfume (Esther 2:12; Ps. 45:8; Prov. 7:17).
   It was a custom of the Jews to give those who were condemned to
   death by crucifixion "wine mingled with myrrh" to produce
   insensibility. This drugged wine was probably partaken of by the
   two malefactors, but when the Roman soldiers pressed it upon
   Jesus "he received it not" (Mark 15:23). (See GALL.)

     This was the gum or viscid white liquid which flows from a
   tree resembling the acacia, found in Africa and Arabia, the
   Balsamodendron myrrha of botanists. The "bundle of myrrh" in
   Cant. 1:13 is rather a "bag" of myrrh or a scent-bag.

     (2.) Another word _lot_ is also translated "myrrh" (Gen.
   37:25; 43:11; R.V., marg., "or ladanum"). What was meant by this
   word is uncertain. It has been thought to be the chestnut,
   mastich, stacte, balsam, turpentine, pistachio nut, or the
   lotus. It is probably correctly rendered by the Latin word
   ladanum, the Arabic ladan, an aromatic juice of a shrub called
   the Cistus or rock rose, which has the same qualities, though in
   a slight degree, of opium, whence a decoction of opium is called
   laudanum. This plant was indigenous to Syria and Arabia.