Announce a study session for your student club to practice a specific set of vocabulary. Choose specialized language for the major being studied by the club and hold an informal spelling bee once a month. Have a grand prize -- perhaps an item with your college logo on it -- to give to the winner of each month's bee.
Hold a game in which your club sits in a circle and one person offers a word within the shared vocabulary of your shared major. The next person has to spell the other person's word out loud and then offer a new word that starts with the same letter with which the last word ended. For example, an anthropology student might start with "epistemological," the second student would spell "epistemological" and then that same student would offer a new word to the next person such as "linguistics." Anyone who spells a word wrong or cannot think of a new vocabulary word is "out."
Play spell or dare, in which students of your club are given complex words to spell. If they get the word right, they can be the next to offer a word. If they get the word wrong, they have to take the "dare," or challenge agreed upon ahead of time by the group. The dare should be feasible, acted on within the moment and inside the room, and should avoid any harm or embarrassment for the people present. For example, a biology student might misspell "integumentary" and have to recite all of the major systems of the human body or list the names of the classification systems for living organisms.
Write the summarized definitions of each vocabulary word on 3-by-5 index cards and shuffle them. These words should form a specialized lexicon provided by the group. Let each person take turns selecting a card. That person reads the definition out loud to the group, and the first person to call out the word gets a chance to spell it. If the person correctly spells the word, the speller gets to pick the next card. If the speller is incorrect, the person next to the reader pulls the next card. Keep practicing until the group has finished the "deck" of cards. Add to the deck with new material learned in classes throughout the term and remove cards from the pile that everyone understands well, but keep them safe in case new members join and need to practice.