The Flocko is a Hardmode, post-Planteraenemy that spawns during the Frost Moonevent. It spawns during waves 11 and later, tending to spawn along with the Ice Queen. It flies towards the player at high speed. Defeating a Flocko does not reward any points / rewards 5 points during the Frost Moon event.
Flock is a short pulverized fiber that can be used to create a velvety coating on objects, such as the spray-on snow used to decorate Christmas trees.
The name may also refer to the French "flocon" or the German "Flocke" (more properly "Schneeflocke"), both meaning "snowflake".
On the achievement for reaching the 15th wave of the Frost Moon, called Ice Scream, the Flocko appears to be on the picture.
It has one of the lowest defenses of any Hardmode enemy, with only 8 defense.
The Bestiary entry for the Flocko: "These ferocious flakes are the frozen minions of the Ice Queen. Where this sinister snow falls, so shall her icy judgment."