n (architecture) A concave vault or archway, especially the arch of a ceiling. (defdate|from 16th c.)
n A small coastal inlet, especially one having high cliffs protecting vessels from prevailing winds. (defdate|from 16th c.)
n (context|now|_|dialectal) A recess or sheltered area on the slopes of a mountain. (defdate|from 19th c.)
n (nautical) A thin line, sometimes gilded, along a yacht's strake below deck level. (defdate|from 19th c.)