guisˈer or guisˈard, also guizˈer noun (chiefly Scot)

1. A person in disguise, dressed up in costume
2. A Christmas (or now usu Hallowe'en and, in Shetland, Up-Helly-Aa) mummer
3. Someone who goes guising

guiˈsing noun

Esp in Scotland, an activity, developed from the tradition of mumming, whereby children dress up and go from house to house collecting cash in return for some musical performance, etc