It is not so important that the students learn the words as they are not commonly used, but to express themselves in a convincing way when they are explaining their definitions. It is based on the old TV game.
A number of cards with the definitions of words on them.
I divide the class up into pairs or groups of three. I write a word that nobody could be expected to know. One word I often choose is "otiose", which means "useless, or serving absolutely no purpose".
I explain the word in three ways, for example saying that it means "very smelly" (another adjective) and "a tool for making potato rings" (a noun). The students try to guess the right meaning.
After this example I give words to the groups on small pieces of paper, with definitions that are slightly simplified, not just dictionary definitions. The groups then think of two false meanings for their words. I draw a table on the board with the names of the groups at the top and down the side and keep score and record the genuine definitions.