means Visual art created in public spaces — murals, stencils, paste-ups, graffiti — often unsanctioned, made to be seen by everyone rather than hung in a gallery.

from A plainly built compound of "street" and "art," rising to common use in the late 20th century as graffiti culture spread from New York subways outward. "Street" descends from Old English "strǣt," itself borrowed from Latin "strāta" (via strāta, a "paved" road) — so the word literally points to the paving stones. "Art" comes through Old French from Latin "ars, artis," skill or craft. The phrase gained gallery respectability as the work moved from being scrubbed off walls to being sold off them.