The Collaborative International Dictionary of English v.0.48:

Sis \Sis\, n.
   A colloquial abbreviation of Sister.
   [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Sis \Sis\, n.
   Six. See Sise. [Obs.] --Chaucer.
   [1913 Webster] Sisal grass

WordNet (r) 3.0 (2006):

sis
    n 1: a female person who has the same parents as another person;
         "my sister married a musician" [syn: sister, sis] [ant:
         blood brother, brother]

V.E.R.A. -- Virtual Entity of Relevant Acronyms (February 2016):

SIS
       Schengen Information System (police, Europe)


V.E.R.A. -- Virtual Entity of Relevant Acronyms (February 2016):

SIS
       Silicon Integrated Systems [corp.] (manufacturer, Taiwan)


V.E.R.A. -- Virtual Entity of Relevant Acronyms (February 2016):

SIS
       Stellen-Informations-Service (WWW)


V.E.R.A. -- Virtual Entity of Relevant Acronyms (February 2016):

SIS
       Software Information Services


V.E.R.A. -- Virtual Entity of Relevant Acronyms (February 2016):

SIS
       Strategic Information System