Acting relaxed can be achieved in different ways with a variety of synonyms. One might opt to appear calm, composed, or at ease. Alternatively, one could come across as nonchalant, unruffled, or blase. If one wants to project an air of minimal effort, it might be wise to act casual or laid-back. For a more formal setting, being poised or dignified would be more appropriate. Acting tranquil, serene, or peaceful when dealing with others could denote a sense of composure in the face of stress. Being easy-going, effortless or relaxed might also be suitable depending on the situation. Ultimately, there are several synonyms to use when trying to act relaxed, with each one conveying slightly different connotations.