| Acronym | Definition |
|---|
| CLASH | Citizens Lobbying Against Smoker Harassment (New York, NY) |
| CLASH | Cluster Lensing and Supernova Survey with Hubble (astronomy) |
| CLASH | Coalition of Lavender Americans on Smoking and Health (est. 1991; various locations) |
| CLASH | Central London Action on Street Health (HIV prevention and outreach; England, UK) |
| CLASH | Cape, Land and Sea Harvest (Cape Cod, MA) |
| CLASH | Association for Children with Language, Speech and Hearing Impairments of Namibia |
| CLASH | Crest Level Assessment of Coastal Structures By Full Scale Monitoring, Neural Network Prediction and Hazard Analysis on Permissible Wave Overtopping |
| CLASH | Character Leadership Attitude Stature Heart (various organizations) |