HB stands for Hot Babe (or sometimes Hunny Bunny) and refers to an attractive women. Usually, the Hot Babe in question has a number assigned to them which corresponds with their perceived attractiveness on a scale of 1-10. So a super hot girl might be described as a ‘HB9’ or ‘HB10’.
The abbreviation from Hot Babe to HB is most commonly used in the online pick-up community, where guys will write about their experiences (called, ‘field reports’) and is used as part of a vast PUA language. The assigned number can also be used to indicate the girl’s social value or personality, rather than just exclusively her looks.
In addition to the assigned number, a short description can also be used to provide further detail to a field report. For example, if a guy is describing two different girls that he deemed to both be ‘8s’, he might refer to one as HB8 Blue Eyes, and the other HB8 French Chick. This is just some basic additional information used to discern between two different girls as part of a story, and can be a reference to almost anything related to the girl, such as height, what she is wearing, where she is from, something she did or said during the interaction etc… etc…
It should be noted that referring to girls as HB’s (plus a number) is considered dubious practice and largely demeaning and derogatory towards women. At the same time, it is a useful – if not preferable – way of abbreviating a story in written form. Referring to girls as HB6’s, or HB (insert any number) verbally is not only judgemental and potentially offensive, but also slightly strange. Most people don’t talk in this kind of way and as such it should be confined to the online forums rather than real life.