No one would argue that defining variables clearly and in an unambiguous manner is critical to good research. With that in mind, work as a group and define the following variables. Keep track of how different people's definitions reflect their personal views of what the variable represents, and note how easy it is to define some variables and how difficult it is to define others.
Intelligence
Height
Social skills
Age
Aggressiveness
Conservatism
Alcohol consumption
Street smarts
Personality
Be sure to note that even those variables that appear to be easy to define (e.g., height) can take on different meanings and definitions (tall, 5 feet 1 inch, awesome) as well.