1. a long essay on a particular subject, especially one written as a requirement for the doctoral degree
Usage: academic
2. a formal discourse or treatise in which a subject is discussed at length

Examples

• She spent three years writing her dissertation on medieval literature.
• The doctoral candidate defended her dissertation before a committee of professors.
• His dissertation examined the effects of climate change on coastal ecosystems.
• The professor assigned a 20-page dissertation on economic theory.
• After completing her dissertation, she was awarded a Ph.D. in psychology.
• The library has a collection of dissertations from graduate students.
• Writing a dissertation requires extensive research and original analysis.