Source : Webster's Revised Unabridged Dictionary (1913)

Sensor \Sen"sor\, a.
   Sensory; as, the sensor nerves.

Source : WordNet®

sensor
     n : any device that receives a signal or stimulus (as heat or
         pressure or light or motion etc.) and responds to it in a
         distinctive manner [syn: {detector}, {sensing element}]

Source : Free On-Line Dictionary of Computing

sensor
     
         An electronic device used to measure a physical
        quantity such as temperature, pressure or loudness and convert
        it into an electronic signal of some kind (e.g a voltage).
        Sensors are normally components of some larger electronic
        system such as a computer control and/or measurement system.
     
        Analog sensors most often produce a voltage proportional to
        the measured quantity.  The signal must be converted to
        digital form with a {ADC} before the CPU can process it.
     
        Digital sensors most often use serial communication such as
        {EIA-232} to return information directly to the controller or
        computer through a {serial port}.
     
        (1997-04-15)