To act, conduct oneself in a specific manner; used with an adverbial of manner.
To act in a polite or proper way.
To conduct (oneself) well, or in a given way.
To act in a tricky, inconstant way, saying one thing and doing another.
To be recklessly inaccurate, inappropriate, or otherwise ignoring guidelines and conventions.
To ignore proper behavior or social conventions, especially when it suits one's purpose.