Sentence:  When you have mastered plainsies, the regular jack game, and have learned all the rules, you will be ready to use this part of the book. A <WSD>fancy</WSD> is a variation of plainsies which usually requires more skill than plainsies does. 
Meaning of the word marked with <WSD> tags:  In the game of jacks, a style of play involving additional actions (contrasted with plainsies).