the open air, especially the daylight of outdoors.
Fine Arts. the quality of light and atmosphere out of doors, especially this quality as rendered in painting.
Origin of plein air
1890-95; < French: literally, full air
[pleyn-air; French ple-ner] /ˌpleɪnˈɛər; French plɛˈnɛr/
pertaining to a manner or style of painting developed chiefly in France in the mid-19th century, characterized by the representation of the luminous effects of natural light and atmosphere as contrasted with the artificial light and absence of the sense of air or atmosphere associated with paintings produced in the studio.
designating a painting executed out of doors and representing a direct response to the scene or subject in front of the artist.
(of a painting) having the qualities of air and natural light.