There's a brief warning before any enemy attack, either quite visible pull back before striking or other style of readying a weapon or possibly just an angry flash of color.
Alternate names: Telegraphed attacks
Name variations: attack telegraphing
The first video game about Attack warning was released on October 14, 2008.
If this behaviour is limited to only few enemies (the above quirk inverted), then this tag is not really appropriate.
This is not for warnings about enemies appearing.