For this achievement, you need the game to roll a yellow die. Play solo so that only you are going for the achievement. When the yellow card is picked, you must spell a 3-5 letter word in 5 seconds. You must be very quick to do this.
Getting a 3 letter word will be easier of course, but sometimes, after you have spelled a word, you can restart the game and the same word will be chosen during the the next match. This does not always work but sometimes does and will make this achievement easier on you.