In the context of AI, an agent is a decision making and acting system that can interact with its environment and other agents.
ETSI GR ENI 004 computational process that implements the autonomous, communicating functionality of an application
ISO/IEC DIS 22989 automated entity that perceives its environment and takes actions to achieve its goals.
Note 1 to entry: An AI agent is an agent that maximizes its chance of successfully achieving its goals by using AI techniques.