thin out
phrasal verb.phrasal verb. to make something less crowded or dense by removing some parts; it also describes when a group of people starts to leave so there are fewer left.
phrasal verb. to reduce the number or density of something in a specific area; can be used transitively (to remove items) or intransitively (to become less numerous).
The crowd begins to thin out after the main event.
You should thin out the seedlings in the garden so the strongest plants have more room to grow.
As the mist began to thin out, the jagged peaks of the mountain range finally became visible to the rescue team.
often used in gardening, hair care, or describing crowds and traffic.
use the image of a forest or a head of hair to explain density; contrast with 'thicken' as the natural opposite process.
Last updated July 28, 2026