WordNet (r) 3.0 (2006):

runaway robin
    n 1: trailing European aromatic plant of the mint family having
         rounded leaves and small purplish flowers often grown in
         hanging baskets; naturalized in North America; sometimes
         placed in genus Nepeta [syn: ground ivy, alehoof,
         field balm, gill-over-the-ground, runaway robin,
         Glechoma hederaceae, Nepeta hederaceae]