The Collaborative International Dictionary
Ambigu \Am"bi*gu\, n. [F., fr. ambigu doubtful, L. ambiquus. See Ambiguous.] An entertainment at which a medley of dishes is set on at the same time.
Wiktionary
n. (context dated English) An entertainment at which a medley of dishes is set on at the same time; a buffet.
Wikipedia
Ambigu is a French card game, composed of the characteristic elements of whist, bouillotte and piquet. A whist pack with the court cards deleted is used, and from two to six persons may play. Each player is given an equal number of counters, and a limit of betting is agreed upon.
Ambigu is a French term that was adopted to mean 'a mixture of things' relating to a type of meal that was popular amongst the English upper class during the mid-17th and mid-18th centuries. It was an evening meal that was less formal than dinner but still planned with a set table and varied types of cold food at the sideboard.