(Internet, informal) A signature, especially one on emails or newsgroup postings.
Your sig should ideally be four or five lines long, six or seven at the maximum. Since it will be repeated on hundreds of messages, a long signature wastes bandwidth and is therefore rude. 1995, Vince Emery, How to grow your business on the Internet:
Posting good content is the best way to get people clicking your sig link. 2004, Brad Hill, Building Your Business with Google For Dummies, page 48:
(intransitive, qualifier:African-American Vernacular, slang) To good-naturedly make fun of someone; to signify.
Those siggin' are also master wordsmiths. They have a variety of concepts to choose from in their rhetorical tool bags. 2010, Ronald L. Jackson II, editor, Encyclopedia of Identity, Thousand Oaks, C.A.: SAGE Publications, Inc., →ISBN, page 730, column 1:
And it is a matter of pride. No Black person wants to be "sigged" about or capped all over. 1969 September, Carolyn M[arie] Rodgers, “Black Poetry—Where It's At”, in Negro Digest, volume XVIII, number 11, Chicago, I.L.: Johnson Publishing Company, Inc., →OCLC, page 16:
Clearly, signifying ain't lost a beat on the bumpy ride from Africa to America. In fact, it seem like brothas been sigging since they stepped off the boat. 2005, Kermit Ernest Campbell, Gettin' Our Groove On: Rhetoric, Language, and Literacy for the Hip Hop Generation, Detroit, M.I.: Wayne State University Press, →ISBN, page 29:
(qualifier:university slang) Sigma (in the names of Greek-letter organizations).
My time at Sig Nu was quite brief, unfortunately, so I'll do my best with the data I gathered. 2022 October 6, Eliza Josephson, “POV: You're dancing at a Yale Frat, or not”, in Yale Daily News, archived from the original on 13 Oct 2022:
Here are 6 of the most cartoonishly sexist, aggressive, and straight-up nuts fraternity and sorority email chains ever released to the public. Let them be a warning to young Kappa Sigs everywhere. 2014 May 29, Prachi Gupta, “Your fraternity email chain will come back to haunt you”, in Salon.com, archived from the original on 13 Dec 2023:
Sig Chi; Kappa Sig; Sig Nu
Outright banning fraternities, however, is a tough move for a university president to make. Greek alums tend to be big donors. [Phil] Hanlon has shied away from making his reform all Greek life, no doubt to avoid the ire of deep-pocketed former Sig Chis. 2014 April 17, Allie Jones, “After Years of Bad Press, the Great Fraternity Crackdown Is Here”, in James Bennet, editor, The Atlantic, Washington, D.C.: The Atlantic Monthly Group, →ISSN, →OCLC, archived from the original on 25 Mar 2023:
(abbreviation, alt-of, humorous, slang) Short for sigma in phrases like "what the sigma"