▪ I.cœlo-1|ˈsiːləʊ|before a vowel cœl-, combining form of Gr. κοῖλος hollow, in various scientific terms, as ˈcœlodont, a.[Gr. ὀδούς, ὀδοντ- tooth], hollow-toothed (epithet of certain lizard-like reptiles as distinguished from the pleodont or solid-toothed). cœloˈrrhizous, a.[Gr. ῥίζα root], having hollow roots. cœloˈrrhyncous, a.[Gr. ῥύγχος beak], hollow-beaked (Syd. Soc.Lex.). † cœˈlostomy[ad.Gr. κοιλοστοµία, f. στόµα mouth], hollowness of voice (cf. celostomy). Also cœlacanth, cœlosperm, etc.1678Phillips (App.), Coelostomie, a speaking with a hollow voice.1727Art of speaking in Publick 64 (Jod.) There is another vice of speaking..which the Græcians have called cœlostomy; it consists in mumbling, when a man does not open his mouth wide enough for his words.▪ II.cœlo-2properly cælo-, combining form of L. cælum, long spelt cœlum sky, heavens, as in cœˈlometer[see -meter], see quot.cœlonaviˈgation, a term proposed for navigation by observation of the heavens (opp. to geo-navigation).1883Fisheries Exhib.Catal. 30 Cœlometer for illustrating nautical Astronomy.