Buff/bʌf/ Definition 1 of 4Pro Tip 1/3Expert Enthusiasm Shows deep knowledge and passion for a subject, usually used positively. My uncle's a tech buff; he can talk for hours about the latest gadgets. Pro Tip 2/3Casual Conversations Common in informal chat, especially when sharing interests. Are you a movie buff? I'd love some recommendations! Pro Tip 3/3Not Professional Refers to hobbyists, not necessarily professionals in the field. She's a gardening buff, with the most beautiful roses on the street.