To delineate means to describe or outline something clearly and precisely, showing exactly what it is or where its boundaries are. When a teacher delineates the rules for a group project, she spells out exactly what students can and can't do, leaving no confusion about expectations. When a map delineates the border between two countries, it shows the precise line where one nation ends and another begins.

The word suggests careful attention to detail and clarity. A scientist might delineate the steps of an experiment so others can repeat it exactly. An author might delineate a character's personality by describing specific behaviors and choices. When you delineate something, you're not being vague or general: you're drawing clear lines, like tracing the outline of your hand on paper.

If your parents delineate your responsibilities for taking care of the family dog, they're making it crystal clear what you need to do: feed the dog twice daily, walk it every afternoon, brush it on weekends. No confusion, no wiggle room, just a clear picture of what's expected.