Holocaust denial

Hilda Doolittle, also known as H.D., an American poet

Attention-deficit hyperactivity disorder, known as Hyperactivity Disorder (HD), as in AD/HD

Harmonisation Document, a normative document in the European Union

Huntington's disease

Harley-Davidson, an iconic American motorcycle manufacturer

Hilary Duff, a music artist

Hodgkin's disease

HD Radio, an abbreviation from the term Hybrid Digital/analog radio

Hormone disruptor

Hip Dysplasia

Home Depot, a chain of home improvement warehouse retailers

the chemical warfare agent sulfur mustard, which in its distilled form is referred to as HD

HD Photo, an image format

Hybrid drive, a type of notebook computer hard drive that utilizes a large buffer

Hokkaido International Airlines, a Japanese low-cost airline with IATA designator HD

Handelshøjskolernes erhvervsøkonomiske Diplomuddannelse, a Danish evening course for a Graduate Diploma in Business and Administration

Higher Diploma, an academic award

Headphone Dust, a record label run by music artist Steven Wilson

HD, a human gene that makes a protein called huntingtin which plays an important role in Huntington's disease

Hard drive, a computer device which stores digitally encoded data, also known as HDD

Henry Draper Catalogue, a sequential numbering system for stars ordered by right ascension

High-definition, in reference to high-definition video, high-definition television (HDTV), or Intel High Definition Audio

High density, in reference to a floppy disk, other magnetic media or the optical formats HD DVD and Blu-ray

Hit Dice, a statistic related to hit points, indicating role-playing game characters' health or durability