There are numerous styles and approaches to photographic (people) portraiture. Someof the categories are classical/traditional, theatrical/glamour, abstract, candid journalistic, or whatever you like or can conjure up creatively. Each has many sub-categories and stylizations.
If I had to come up with a simple definition it would be"an image that makes a VISUAL statement about a person". The system is in the hands and eyes of the photograher. For example- low key portrait of a lovely lad- dark dress- dark background, etc- hs emphasizes the face and perhaps the body. The statement is perhaps "A lovely lady". If we were to change the dress to a bright fluorescent red dress or a more revealing outfit, the STATEMET may change to "a glamourous red or sexy dress, with and lovely lady in it- perhaps an entertainer or a model" The latter may be considered by some a "glamour" portraot or starting to look like a fashion shot. Ain't anythg wrong with that interpretation unless she was using the image to accompany her application for the position of a school teacher or a nurse? Tattoos, untraditional clothing, whatever, are all part of a person's personality self-image, or image they wanted to project.
Props, and background details, are elements that help tell a story about the subject.
In traditional portraiture, the subject (client) usually wants a flattering interpretation. Therein lies the artistry! It's hard work and ain't for the impatient or faint of heart. I can write a book but my typing in lousey!
I have been in the portrait business all my working life and have never had a client ask me for anything that would be considered pornographic or in poor taste.
For me- a good portrait consists of a good likeness, a natural expression and pose, and effective lighting.
If anyone out there is interested in fine portraiture- don't bother to define it. Bone up on your people skills, lighting, and camera technique, and photograph PEOPLE- as many as you can! Make those statements!
"Cheesecake" is good eating! A "hot babe" is an infant running a fever! STOP Already with the outdated lingo- what is this- the 7th grade?