The Collaborative International Dictionary of English v.0.48:

Chop suey \Chop su"ey\ or Chop sooy \Chop soo"y\ . [Chin.
   (Cantonese) shap sui odds and ends, fr. shap for sap to enter
   the mouth + sui small bits pounded fine.]
   A m['e]lange served in Chinese restaurants to be eaten with
   rice, noodles, etc. It consists typically of bean sprouts,
   onions, mushrooms, etc., and sliced meats, fried and flavored
   with sesame oil. [U. S.]
   [Webster 1913 Suppl.]

WordNet (r) 3.0 (2006):

chop suey
    n 1: meat or fish stir-fried with vegetables (e.g., celery,
         onions, peppers or bean sprouts) seasoned with ginger and
         garlic and soy sauce; served with rice; created in the
         United States and frequently served in Chinese restaurants
         there