Loose cannon is a term used to describe someone who lacks restraint, is unpredictable and behaves in an uncontrolled manner. An antonym for this term would be a person who is calm, collected, and measured in their behavior. Such a person is reliable, trustworthy, and dependable, even in challenging situations. They are also known for their stability and adherence to rules and regulations, making them a valuable asset in any team or organization. The antonyms of the word "like loose cannon" could be steady, cautious, trustworthy, reliable, or consistent. These qualities are highly sought after in individuals who are tasked with responsibility in personal or professional settings.