S.a. Definition

abbreviation
Without year or date.
Webster's New World
South Africa.
Wiktionary
South America.
Wiktionary
Sub anno.
Wiktionary
(dated) Sex appeal.
Wiktionary
letter

The nineteenth letter of the English alphabet, called ess and written in the Latin script.

Wiktionary
numeral

The ordinal number nineteenth, derived from this letter of the English alphabet, called ess and written in the Latin script.

Wiktionary
noun

American Library Association. Abbreviation for sextodecimo, a book size, 15-17.5 cm in height.

Wiktionary