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n. pl. os·ti·a (-tē-ə)
1. A small opening or orifice, as in a body organ or passage.
2. Any of the small openings or pores in a sponge, through which water is drawn in.
American Heritage® Dictionary of the English Language, Fifth Edition. Copyright © 2016 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.
n, pl -tia (-tɪə)
1. (Zoology) any of the pores in sponges through which water enters the body
2. (Zoology) any of the openings in the heart of an arthropod through which blood enters
3. (Biology) any similar opening
[C17: from Latin: door, entrance]
Collins English Dictionary – Complete and Unabridged, 12th Edition 2014 © HarperCollins Publishers 1991, 1994, 1998, 2000, 2003, 2006, 2007, 2009, 2011, 2014
os•ti•um(ˈɒs ti əm)
n., pl. -ti•a (-ti ə)
a small opening or orifice of the body.
[1655–65; < Latin ōstium entrance, river mouth]
Random House Kernerman Webster's College Dictionary, © 2010 K Dictionaries Ltd. Copyright 2005, 1997, 1991 by Random House, Inc. All rights reserved.