1.
1 : to move irregularly or unsteadily : flutter Shadows flickered on the wall.
2 : to burn or shine fitfully or with a fluctuating light

a candle flickering in the window
3 : to appear or pass briefly or quickly

Thoughts flickered through his mind. A smile flickered across her face.
4 : to cause to flicker
5 : to produce by flickering
6 : an act of flickering
7 : a sudden brief movement

the flicker of an eyelash
8 : a momentary quickening

a flicker of anger
9 : a slight indication : hint a flicker of recognition
10 : a wavering light

the flicker of a candle
11 : a repeated momentary defect in a cathode-ray tube image caused especially by slow scanning of the screen
12 : movie —often used in plural
13 : a large barred and spotted North American woodpecker (Colaptes auratus) with a brown back that commonly forages on the ground for ants — compare red-shafted flicker, yellow-shafted flicker
14 : to burn or glow in an unsteady way : to produce an unsteady light
15 : to appear or pass briefly or quickly
16 : to burn unsteadily

a flickering candle
17 : to appear briefly

A smile flickered across her face.
18 : to move quickly

Roy's eyes flickered to her hand …— Carl Hiaasen, Hoot
19 : a quick small movement

a flicker of the eyelids
20 : a quick movement of light
21 : a large North American woodpecker
22 : the wavering or fluttering visual sensation produced by intermittent light when the interval between flashes is not small enough to produce complete fusion of the individual impressions