Definition of sis
(Entry 1 of 3)
: sister
—usually used in direct address
SIS
abbreviationDefinition of SIS (Entry 2 of 3)
Secret Intelligence Service
Note: The Secret Intelligence Service is a British government agency that is responsible for the collection and analysis of information about foreign countries or groups.
-sis
noun suffix
plural -ses
Definition of -sis (Entry 3 of 3)
: process : action
peristalsis
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Merriam-Webster unabridged
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Time Traveler for sis
The first known use of sis was in 1596
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