A great way to improve your vocab is by making a game out of it.
More than 4500 words.
The objective of the game is to bring the average score from 5.0 to 10.0.
Initially all the words have a score of 5.0 which makes the average score 5.0. When you play the game there will be a series of questions and each question has four possible options. If you guess the answer correctly, the score of that word gets increased by 1 (to a maximum value of 10). If enough words are guessed correctly the average score will move up.
Likewise if the words are guessed incorrectly, the average score will decrease.
Words having a lesser score will appear more frequently.
Also words that you have learnt the meaning of, you can mark them as learnt, so that they do not appear as a part of the game. They will be treated as having a score of 10.0. You can mark/unmark the words as learnt from the word list.
Useful app for: GRE GMAT CAT SAT TOEFL IELTS
Added "Show Meaning" in the game mode so that people can use this game as a learning tool.