The Collaborative International Dictionary of English v.0.48:

Bay tree \Bay" tree`\
   A species of laurel. (Laurus nobilis).
   [1913 Webster]

WordNet (r) 3.0 (2006):

bay tree
    n 1: small Mediterranean evergreen tree with small blackish
         berries and glossy aromatic leaves used for flavoring in
         cooking; also used by ancient Greeks to crown victors [syn:
         true laurel, bay, bay laurel, bay tree, Laurus
         nobilis]

Easton's 1897 Bible Dictionary:

Bay tree
   named only in Ps. 37:35, Authorized Version. The Hebrew word so
   rendered is _ereh_, which simply means "native born", i.e., a
   tree not transplanted, but growing on its native soil, and
   therefore luxuriantly. If the psalmist intended by this word to
   denote any particular tree, it may have been the evergreen bay
   laurel (Laurus nobilis), which is a native of Palestine. Instead
   of "like a green bay tree" in the Authorized Version, the
   Revised Version has, "like a green tree in its native soil."