The Collaborative International Dictionary of English v.0.48:

Sillabub \Sil"la*bub\, n. [Cf. sile to strain, and bub liquor,
   also Prov. E. sillibauk.]
   A dish made by mixing wine or cider with milk, and thus
   forming a soft curd; also, sweetened cream, flavored with
   wine and beaten to a stiff froth. [Written also syllabub.]
   [1913 Webster]

WordNet (r) 3.0 (2006):

sillabub
    n 1: spiced hot milk with rum or wine [syn: syllabub,
         sillabub]
    2: sweetened cream beaten with wine or liquor [syn: syllabub,
       sillabub]