Dictionary.com
definitions

-stat

a combining form used in the names of devices that stabilize or make constant what is specified by the initial element: thermostat; rheostat.

Origin of -stat

< Greek -statēs, equivalent to sta- (stem of histánai to make stand; see stand) + -tēs agent noun suffix
Dictionary.com Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2019
British Dictionary definitions for -stat

-stat

n combining form

indicating a device that causes something to remain stationary or constantthermostat

Word Origin for -stat

from Greek -statēs, from histanai to cause to stand
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
Word Origin and History for -stat

combining form used in forming the names of devices for stabilizing or regulating (thermostat, etc.), from Greek statos "standing, stationary," from histanai "to cause to stand," from PIE root *sta- "to stand" (see stet). First used in heliostat "an instrument for causing the sun to appear stationary" (1742).

Online Etymology Dictionary, © 2010 Douglas Harper
-stat in Medicine

-stat

suff.

Something that stabilizes:barostat.
Something that inhibits:hemostat.
The American Heritage® Stedman's Medical Dictionary Copyright © 2002, 2001, 1995 by Houghton Mifflin Company. Published by Houghton Mifflin Company.