Added 9 October 2026 coastline noun Categories: PlacesRare Words noun ! Definition from WordNet 3.1, Princeton University. More about coastline at Wordnik → Where our words come from → The outline of a coast. Origin From coast + line. From Wiktionary, via Kaikki.org (CC BY-SA) Related Words: coastcoastalseashoreseaboardforeshoreseacoastshorelineseasideinshoreshorebeachmarine Back to today's word