Definition from Wiktionary, the free dictionary
- An alternative word for floccule. A soft or fluffy particle suspended in a liquid or the fluffy mass of suspended particles so formed. Floc may be mineral as for clay, chemical as in water treatment or biological as in sewage treatment.
From Latin floccus.
declension of floc
Usage notes 
This word can also function in the neuter gender, with the plural form floace.