Definition of "Scanner" :
noun: a radio receiver that moves automatically across some selected range of frequencies looking for some signal or condition
"They used scanners to monitor police radio channels."
noun: a radar dish that rotates or oscillates in order to scan a broad area
noun: an electronic device that generates a digital representation of an image for data input to a computer
noun: someone who scans verse to determine the number and prosodic value of the syllables