The Collaborative International Dictionary of English v.0.48:

Mother-of-thyme \Moth"er-of-thyme`\, n. (Bot.)
   An aromatic plant (Thymus Serphyllum); -- called also wild
   thyme.
   [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Thyme \Thyme\ (t[imac]m), n. [OE. tyme, L. thymum, Gr. qy`mon,
   qy`mos; cf. qy`ein, to sacrifice, qy`os a sacrifice,
   offering, incense: cf. F. thym; -- perhaps so named because
   of its sweet smell. Cf. Fume, n.] (Bot.)
   Any plant of the labiate genus Thymus. The garden thyme
   (Thymus vulgaris) is a warm, pungent aromatic, much used to
   give a relish to seasoning and soups.
   [1913 Webster]

         Ankle deep in moss and flowery thyme.    --Cowper.
   [1913 Webster]

   Cat thyme, a labiate plant (Teucrium Marum) of the
      Mediterranean religion. Cats are said to be fond of
      rolling on it. --J. Smith (Dict. Econ. Plants).

   Wild thyme, Thymus Serpyllum, common on banks and
      hillsides in Europe.
      [1913 Webster]

            I know a bank where the wild thyme blows. --Shak.
      [1913 Webster]

WordNet (r) 3.0 (2006):

wild thyme
    n 1: aromatic dwarf shrub common on banks and hillsides in
         Europe; naturalized in United States [syn: wild thyme,
         creeping thyme, Thymus serpyllum]