What is Behavior?

Legal Definition
Behavior is the range of actions and mannerisms made by individuals, organisms, systems, or artificial entities in conjunction with themselves or their environment, which includes the other systems or organisms around as well as the (inanimate) physical environment. It is the response of the system or organism to various stimuli or inputs, whether internal or external, conscious or subconscious, overt or covert, and voluntary or involuntary.

Taking a behavior informatics perspective, a behavior consists of behavior actor, operation, interactions, and their properties. A behavior can be represented as a behavior vector.
-- Wikipedia
Legal Definition
Maimer of behaving, whether good or bsd; conduct; manners; carriage of one's self, with respect to propriety and morals; deportment. Webster. State v. Roll, 1 Ohio Dec. 284. Surety to be of good behavior is said to be a larger requirement than surety to keep the peace.
-- Black's Law Dictionary
Legal Definition
-- Ballentine's Law Dictionary