The process of learning a new word can be a long one. Between encountering a word for the first time and being able to use the word in speaking and writing, students must acquire many different kinds of knowledge about the word. The first step, however, is to look for a definition. How do teachers and students define words? What are common mistakes that are made when defining words, and how can teachers and students define words effectively? In order to investigate these questions, we conducted a survey on dictionary use for intermediate and advanced learners in academic university programs. We also interviewed teachers and observed various classes at the postsecondary level focusing on vocabulary and word learning strategies. We first noted some of the most common difficulties that teachers and students encountered when defining words. From our findings, we compiled points of practical advice to inform teachers and students of how to approach defining words.