Initialism of Smithsonian Institution.

(electronics) Initialism of signal integrity. / (technology) Initialism of systems integration. / Initialism of self-injury.

(anatomy, medicine) Initialism of sacroiliac.

(music) A syllable used in solfège to represent the seventh note of a major scale.

A diminutive of the male given name Simon. / A diminutive of the male given name Silas.

(historical) Various prefectures of imperial China.

Alternative form of Xi

(Britain) Initialism of Secret Intelligence Service. / Initialism of Schengen Information System.

Initialism of second impact syndrome. / Initialism of snow immersion suffocation. / (education) Initialism of student information system. / Initialism of supervised injection site.

(informal) Clipping of sister.