Write a word on the board that the students have never heard. They must each write what they think the definition is. Have the students read their definitions and vote for the one they think is correct. After they do that, reveal the definition. If there are too many students for this game to work properly, write a word on the board and have students orally try to guess the definition of it.
Distribute one of the same dictionary to each child in the class, and have them all turn to the same page in that dictionary. Distribute a crossword puzzle that correlates with the page in the dictionary. Using the clues from the puzzle and the dictionary, students must figure out which word from the page belongs in each space. You could also have students do a word find that corresponds to one page from the dictionary.
Use a dictionary as a tool for a scavenger hunt. Divide the class into teams or allow students to work on their own, as long as there is a dictionary for each child. Distribute a handout with questions on it such as "What is the 10th word in the dictionary?" and "Who wrote this dictionary?" You should also provide definitions for words, without the actual words, and ask them to find the word the definition belongs to.
Bring the students to the computer lab and allow them to play some online games for a class period. Allow them to visit the Game of the Week, provided by Merriam-Webster. Word Plays has a vast number of dictionary-related games on it. Some examples of their games include anagrams, cryptograms and words in words. Allow students to refer to a dictionary for help, if the game doesn't require direct use of a dictionary.