This can be a high-stress question if you are not prepared to discuss your personality and characteristics. Rather than freezing up during your interview or saying something you regret, take a few minutes to jot down some ideas before your meeting.
Review AECOM's website. They state on their career page that they are looking for intellectually curious employees, entrepreneurial spirits, team players, and unique talents. Comb through every page of their website. Familiarize yourself with all the different aspects of their company. Use recurring keywords from the job postings or the 'About Us' section. These recurring themes and keywords will give you a great idea of the personality and characteristics that AECOM is looking for.