| Acronym | Meaning |
| HCG | Human Chorionic Gonadotropin |
| HCI | Human-Computer Interface |
| HCI | Highly Charged Ion |
| HCL | Hollow Cathode Lamp |
| HCMOS | High-density Complementary Metal-oxide Semiconductor |
| HCMV | Human Cytomegalovirus |
| HCN | US Historical Climatology Network |
| HCO | Heavy Cycle Oil |
| HCOT | Helically Coiled Open Tube |
| HCP | Hexagonal Close Packed |
| HCPA | Homomorphic Cluster Coherent Potential Approximation |
| HCPT | Hard-core Perturbation Theory |
| HCS | Heliospheric Current Sheet |
| HCS | Hazard Communication Standard |
| HCS | High Content Screening |
| HCSEL | Horizontal Cavity Surface Emitting Laser |
| HCV | Hepatitis C Virus |
| HCWP | Hard Corrugated Wall Potential |
| HD | Sulfur Mustard |
| HD | Hydrogen Damage |
| HDAC | Histone Deacetylase |
| HDC | Hydrodynamic Chromatography |
| HDC | High Dose Chemotherapy |
| HDC | Histidine Decarboxylase |
| HDD | Halogenated Dibenzodioxin(s) |
| HDD | Hard Disk Drive |
| HDEHP | Bis(2-ethylhexyl)phosphoric Acid |
| HDES | Hydrodynamic Equilibrium System |
| HDF | Hubble Deep Field |
| HDF | Halogenated Dibenzofuran(s) |
| HDF | Human Dermal Fibroblast |
| HDF | Human Diploid Fibroblast |
| HDI | High-density Inclusion |
| HDL | High Density Lipoprotein |
| HDM | House Dust Mite |
| HDM | Humic Degradation Matter |
| HDMR | High-dimensional Model Representation |
| HDP | High-density Plasma |
| HDPE | High-density Polyethylene |
| HDPEX | Cross-linked |
| HDR | Hot Dry Rock (geothermal Reservoir) |
| HDS-MAT | Hydrodesulfurization Micro-activity Test |
| HDT | Heat Deflection Temperature |
| HDT | Heat Distortion Temperature |
| HDT | High-dose Therapy |
| HDTBPB | Hexadecyltributylphosphonium Bromide |
| HDTMAB | Hexadexyltrimethylammonium Bromide |
| HDV | Hepatitis Delta Virus |
| HDVV | Heisenberg-Dirac-Van Vleck (Hamiltonian Or Exchange Parameter) |
| HEA | 2-hydroxyethyl Acrylate |