The Collaborative International Dictionary of English v.0.48:

Ambrosian \Am*bro"sian\, a.
   Ambrosial. [R.] --. Jonson.
   [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Ambrosian \Am*bro"sian\, a.
   Of or pertaining to St. Ambrose; as, the Ambrosian office, or
   ritual, a formula of worship in the church of Milan,
   instituted by St. Ambrose.
   [1913 Webster]

   Ambrosian chant, the mode of signing or chanting introduced
      by St. Ambrose in the 4th century.
      [1913 Webster]

WordNet (r) 3.0 (2006):

Ambrosian
    adj 1: of or by or relating to Saint Ambrose; "Ambrosian chants"
    2: extremely pleasing to the taste; sweet and fragrant; "a
       nectarous drink"; "ambrosial food" [syn: ambrosial,
       ambrosian, nectarous]
    3: worthy of the gods [syn: ambrosial, ambrosian]