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]