We found 23 dictionaries that define the word hard water:

General (11 matching dictionaries)

1. hard water: Vocabulary.com
2. hard-water, hard water: Wordnik
3. hard water: Wiktionary
4. hard water: Infoplease Dictionary
5. hard water: Dictionary.com
6. Hard water: Wikipedia, the Free Encyclopedia
7. hard water: Rhymezone
8. hard water: Stammtisch Beau Fleuve Acronyms
9. hard water: FreeDictionary.org
10. hard water: Mnemonic Dictionary
11. hard water: TheFreeDictionary.com

Business (2 matching dictionaries)

12. Construction Term Glossary (No longer online)
13. BusinessDictionary.com (No longer online)

Computing (1 matching dictionary)

14. hard water: Encyclopedia

Medicine (2 matching dictionaries)

15. online medical dictionary (No longer online)
16. hard water: Medical dictionary

Science (1 matching dictionary)

17. Chemistry Dictionary (No longer online)

Slang (1 matching dictionary)

18. Hard Water: Urban Dictionary

Tech (5 matching dictionaries)

19. Lake and Water Word Glossary (No longer online)
20. Schlumberger Oilfield Glossary (No longer online)
21. Pool Glossary (No longer online)
22. HARD WATER: Power Engineering
23. Glossary of Water Resource Terms (No longer online)

(Note: See hard_waters as well.)

Definitions from Wiktionary (hard water) ▸ noun:  (chemistry) Water with a high concentration of dissolved minerals, especially calcium, making it difficult to lather with soap. Similar: hardwater, soft water, water hardness, total hardness, soap scum, hardness, hard soap, limescale, hydrophilite, lightwater, more... Opposite: soft water, non-hard water, low mineral water Types: bicarbonate, sulfate, chloride, nitrate, more... Adjectives: tartar, manganiferous, argentine, schistose, ferruginated, seleniferous, hornfelsed, cherty, gneissoid, ultramafic, argentous ▸ Words similar to hard water ▸ Usage examples for hard water ▸ Idioms related to hard water ▸ Wikipedia articles (New!) ▸ Words that often appear near hard water ▸ Rhymes of hard water ▸ Invented words related to hard water