The topics for a definition research paper are endless (ie: rattlesnakes, cancer, back surgery...).

If you are struggling to find a topic, think of the type of music you like to listen to, the movies you like to watch, the topics in school that interest you... Also, you can refer to the topics on the Argumentative Paper Topics site. These can also be Definition Paper Topics, as long as you do not state your opinion/side on the issue.