"Aggression behavior" refers to actions or conduct that are aggressive or violent in nature. It involves behaving in a way that can cause harm or intimidation towards others.
After 14 days: Your kittens may still be shy, but should be more comfortable with you approaching them and should no longer display defensive aggression behaviors. (bestfriends.org)
A mother might show aggression behavior toward anyone that is perceived to be a threat to the pups. (dog-health-guide.org)