1. An anthropoid which is similar to the monkey, but that is much larger and normally lives in Africa, typically in the forested areas: Almost any gorilla probably has an unhappy life in a zoo as compared to its natural existence in a jungle.
2. An ugly or brutal person: Robert's rude and aggressive manners earned him the reputation of being a gorilla.

Someone who engages in irregular warfare, the goal of which is usually to overthrow a current government: To be successful, a guerrilla must operate in a countryside where there are civilian sympathizers.