In the 1977 edition of the American Heritage Dictionary punk rock was given this wonderful definition:
Punk rock, n. A form of rock music characterized by a stabbing, insistent rhythm and simple, three-chord harmony, amplified sound, and lyrics that deal with subjects full of trouble and strife such as anarchy, alienation, violence, sex, drugs and teen-age rebellion.Featuring photographs by Jenny Lens and modeling by Belinda Carlisle, this 1977 zine How To Look Punk by Marliz is an amazing gem. It's a fascinating document for a number of reasons (besides the photographs of a young pre-Go-Go's Carlisle), including what appears to be Marliz's "note on author," in which she identifies herself as a professional trendspotter: "Marliz is internationally known in the industry for her marketing ability in current-trend perception, and 'how to' help it explode on the scene." This blurb certainly reiterates that just as soon as punk became a "thing" it became a "trend" too.
Punk performers and their followers often adopt outlandishly vulgar behavioral patterns and clothing, often leading to acts of violence by performers and audience alike.