means A device or program that systematically examines something — a page, a barcode, a radio frequency, a body, or a computer's files — converting what it finds into digital information.

from From the verb "scan," which came through Latin "scandere," meaning "to climb" — and, in the world of poetry, "to mark out the rhythm of verse" by stepping through it foot by foot. That methodical stepping-through is the heart of it: to scan once meant to scrutinize line by line. The "-er" turns the act into the actor, and the modern machine sense — eyes that sweep across a surface and record what they see — bloomed in the 20th century alongside television, radar, and computing.