The Collaborative International Dictionary of English v.0.48:
Wassail \Was"sail\, a.
Of or pertaining to wassail, or to a wassail; convivial; as,
a wassail bowl. "Awassail candle, my lord, all tallow."
Wassail bowl, a bowl in which wassail was mixed, and placed
upon the table. "Spiced wassail bowl." --J. Fletcher.
"When the cloth was removed, the butler brought in a huge
silver vessel . . . Its appearance was hailed with
acclamation, being the wassail bowl so renowned in
Christmas festivity." --W. Irving.
Wassail cup, a cup from which wassail was drunk.