Nebulous means vague, unclear, or lacking definite form. When something is nebulous, you can't quite pin it down or see it clearly. A nebulous plan is one without specific details: maybe your friend suggests “we should hang out sometime” but won't say when or where. A nebulous explanation leaves you more confused than before, like when someone describes a movie as “kind of about stuff happening” instead of telling you the actual plot.

Just as you can't grab a handful of fog, you can't get a firm grip on nebulous ideas. When a teacher gives nebulous instructions like “write about something interesting,” students often struggle because they need clearer guidance.

Scientists use nebula to describe actual clouds of gas and dust in space, which can look hazy and undefined through telescopes. But in everyday conversation, calling something nebulous usually means it needs to be clearer and more specific. If your understanding of fractions feels nebulous, you need more practice to make the concept solid and clear in your mind.