Webster’s Revised Unabridged Dictionary · 1913
Leptothrix
Lep′to·thrix (lĕp′tō·thrĭks), n. [NL., fr. Gr. λεπτός small + θρίξ hair.] (Biol.) A genus of bacteria, characterized by having their filaments very long, slender, and indistinctly articulated.
Lep′to·thrix, a. [See Leptothrix, n. ] (Biol.) Having the form of a little chain; — applied to bacteria when, as in multiplication by fission, they form a chain of filiform individuals.