One thing that I do and the students really get into is:
Create a word cloud of the target vocabulary from sites such as:
Each student receives a copy and puts a circle around the words they know and can explain to others. (Be careful because they will try to circle unknown words. Pyschologically they also get a kick out of realising how many words they do know instead of always looking at the negative.)
Next, if they don �t know a word they( student A) must find someone (student B) who has circled a word. The person with the circled word (student B )then teaches the word to Student A. Student A can now in turn teach the new word to student C. It does not have to be done in pairs..there can be groups of 3 or 4 listening to the explanation. It works because every student is involved all the time and they keep repeating the definition thereby reinforcing it.
The teacher must watch out for incorrect definitions.
At the end of the period they must give me one new word they learnt today.
Cheers Joy