One of the practice structures that I like to use to improve vocabulary is Taboo. Here are the Directions from Hasbro for the official game. Basically one player tries to get their teammates to guess as many vocabulary words in a given time as possible. The player chooses a card with the vocabulary word on it as well as several other words that are 'taboo.' The player gives verbal hints to the vocabulary word but can not use the taboo words.
For example, the player would give clues to have their teammates guess the word monomial, but they can not use the clues: polynomial, one, term, or variable. Maybe they would say "single addend" or "you find the degree by adding the exponents on non-numerical bases."
I think this game works best as a review after a very vocabulary heavy lesson or unit. It forces everyone to think of synonyms or descriptions beyond what may have been given in the notes or in the textbook.
My favorite way to use this activity is to have students create the taboo cards. I give the kids about 5 minutes to review the unit for vocabulary words to create their own game card including the taboo words. I have each student put their vocab word and taboo words on a quarter sheet of paper and fold it in half. Then as a class we play using the student generated word by pulling the cards from a shoe box.
Here are three versions of the game that I have created. If you try any of them, please share your feedback.
Grade 4 Vocabulary Taboo
Grade 6 Vocabulary Taboo
Algebra 1 Polynomial Taboo