1) Sauce 2) Sauce of onions 3) White onion sauce 1) Sauce 
• (n.) A sauce made of white onions and melted butter mixed with veloute sauce. • (n.) A kind of cravat worn by men in the late 18th century.
Purée of onions, sometimes mixed with béchamel sauce.
Sou`bise' (sō`bēz') noun 1. [ French] A sauce made of white onions and melted butter mixed with velouté sauce. 2. A kind of cravat worn by men in the late 18th century. 
onion sauce.
onion sauce
[n] - veloute sauce with sauteed chopped onions and whipping cream
white onion sauce noun veloute sauce with sauteed chopped onions and whipping cream