noun, plural ty·lo·ses [tahy-loh-seez] /taɪˈloʊ siz/. Botany.
  1. a bubblelike formation in the cavity of tracheids or vessels in the wood of trees, consisting of protoplasm intruded from adjacent parenchyma cells.
Often ty·lose [tahy-lohs, tahy-lohs] /ˈtaɪ loʊs, taɪˈloʊs/.

Origin of tylosis

1875–80; < Greek týlōsis act of making callous, equivalent to tylō-, variant stem of tyloûn to make callous, hard, derivative of týlos callus, lump, knob + -sis -sis
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British Dictionary definitions for tylosis


  1. botany a bladder-like outgrowth from certain cells in woody tissue that extends into and blocks adjacent conducting xylem cells

Word Origin for tylosis

C19: from Greek tulōsis, from tulos knob or tulē callus + -osis
Collins English Dictionary - Complete & Unabridged 2012 Digital Edition © William Collins Sons & Co. Ltd. 1979, 1986 © HarperCollins Publishers 1998, 2000, 2003, 2005, 2006, 2007, 2009, 2012

tylosis in Medicine


n. pl. ty•lo•ses (-sēz)
  1. Inflammation of the eyelids, characterized by thickening and hardening of the edges.
  2. A thickening of the horny layer of the skin as a result of chronic pressure or friction.
The American Heritage® Stedman's Medical Dictionary Copyright © 2002, 2001, 1995 by Houghton Mifflin Company. Published by Houghton Mifflin Company.