Observe/əbˈzɜːrv/ Definition 1 of 5Pro Tip 1/2Attention to Detail Use when details are crucial, like behavior, or subtle changes that are important to note. The detective observed every move of the suspect. Pro Tip 2/2Not Passive Watching Implies actively watching with focus, not just glancing or seeing casually. In the experiment, we must observe the chemical reaction closely.