phacelia Syllabification: (pha·ce·li·a)Pronunciation: /fəˈsēlēə/Definition of phacelia noun a herbaceous American plant with clustered blue, violet, or white flowers. Genus Phacelia, family Hydrophyllaceae Origin:modern Latin, from Greek phakelos 'cluster'phacelia in other Oxford dictionaries Definition of phacelia in the British & World English dictionary