| HHO | H2o Hydrogen Oxygen
| Others |
| HHO | Hard Hairy One
| Others |
| HHO | Hard Hand Off
| Others |
| HHO | Harris Hawks Optimization
| Others |
| HHO | Harris Hawks Optimizer
| Others |
| HHO | Hava Harp Okulu
| Others |
| HHO | Hawthorne Hangar Operations
| Others |
| HHO | Heat Harvest Ongrid
| Others |
| HHO | Helicopter Hoist Operations
| Others |
| HHO | Helicopter Hoist Operator
| Others |
| HHO | Henry Hadaway Organisation
| Others |
| HHO | Hepatic Hypertrophic Osteoarthropathy
| Others |
| HHO | Home and Home Office
| Others |
| HHO | Home Heating Oil
| Others |
| HHO | Hunterdon Hematology Oncology
| Others |
| HHO | Hybrid Hydrogen Oxygen
| Others |
| HHO | Hydrocarbon Hash Oil
| Others |
| HHO | Hydrogen Hydrogen Oxygen
| Others |