It's usually used in the bracket in the text besides the word which could be recognized as written in the wrong way;
Mostly used to a quoted spelling mistake, implying for the reader that it isn't our mistake, but it was this way in the original.
As he wrote in his message "tihs will be a looong juorney" (sic!);
Most often occurs in white women when confronting her lust/logic conundrum regarding interracial romance. Most often accompanied by a "sick" facial expression upon seeing a black guy that they are attracted to.
Abbreviated form of 'sicosnipophobic'; which is, according to the mockumentary "Rock, Paper, Scissors: The Way of the Tosser", is someone afraid of scissors.
This short form is appealing because it is monosyllabic, as well as being homophonic and alliterative with its opposite, a 'snip'; ie. someone who is /for/ the cuts. The scissors analogy fits as it has become a symbol of the proposed cuts to the budget.
Student #2: What, me? Oh, I'm a sic here. A sic an' proud!
Student #1: Phew, thought you were a snip there.
Student #2: A snip? Don't be daft mate.
Student #1: Yeah, soz. Can't tell whose who sometimes..
If the quotation you are using contains a grammatical error, you may reproduce that error, but you must write "sic" after it to indicate the error is not yours. You may also want to use "sic" after an offensive word or comment that you are quoting to indicate that you do not share the speaker's attitude.
of a ryhming sic peasant strongly or localy sic enough"
(Autobiographical Writings 106).