Quizlet has an auto-define feature that can save you a lot of time when you create a study set. Start typing your term. A small "auto-define" button will appear below the text box:
Click this button to auto-define your term. A window will appear with a selection of user-contributed definitions (including foreign languages), as well as definitions from an online dictionary, sorted by most-used within Quizlet:
Note that user-contributed definitions are marked.
Once you've selected a definition you like, click "Use selected definition." Quizlet will automatically fill in the definition you have selected - no need to type anything!
You can do this for as many terms as you want in your set.