There are 2 definitions of sig in English:

sig1

Syllabification: sig
Pronunciation: /siɡ
 
/

noun

Computing, informal
A short personalized message at the end of an e-mail.
More example sentences
  • How do I tell a friend her email sig is really annoying?

Origin

1990s: abbreviation of signature.

Definition of sig in:

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Word of the day flippant
Pronunciation: ˈflɪp(ə)nt
adjective
not showing a serious or respectful attitude

There are 2 definitions of sig in English:

SIG2

Syllabification: SIG
Pronunciation: /siɡ
 
/

abbreviation

Computing
Special interest group.

Definition of sig in: