What does HGG stand for?

Herpetic Geniculate Ganglionitis - Medicine (DB)

Higginbotham Boat Co., Austin, TX - Manufacturer code for watercraft hull identification number (USCG)

Higginbothan - NCIC boat manufacturer code (NCIC)

Hot Gas Generator

Human Gamma-Globulin - Endocrinology

Human Gas Generator (SAUS)

Hypogammaglobulinaemia (SAUS)