- Initialism of Hansestadt Bremen. The German city of Bremen. (Used on licence plates and informally in other contexts.)
- Let's meet in HB tomorrow.
HB (not comparable)
- hard black (describing a pencil that makes lighter marks than a grade B, but darker marks than a grade H pencil)
HB (plural HBs)
- (stars) Abbreviation of horizontal branch.
- (slang, seduction community) A hot babe, someone pickup artists try to seduce. (Usually followed by a number in the 1-10 scale of physical beauty, e.g. HB10.)
- (health) Initialism of homebirth.
- ZAHB (zero-age horizontal branch)
- BHB (blue horizontal branch)
- AGB (asymptotic giant branch)
- TRGB (tip of the red giant branch)