Definitions of flicker:

• noun:   North American woodpecker
• noun:   a momentary flash of light
• noun:   the act of moving back and forth
• verb:   flash intermittently
• verb:   shine unsteadily

  Example: "The candle flickered"

• verb:   move back and forth very rapidly

  Example: "The candle flickered"

• name:  A surname (very rare: popularity rank in the U.S.: #24673)