plein-air
Concise Oxford English Dictionary © 2008 Oxford University Press:
plein-air /plɛn ˈɛː/
▶adjective denoting or relating to a 19th-century style of painting outdoors which became a central feature of French Impressionism.
– origin from Fr. en plein air ‘in the open air’.
'plein-air' also found in these Oxford entries:

