(sic) (Latin for "thus") is a bracketed expression used to indicate that an unusual spelling, phrase, or any other preceding quoted material is intended to be read or printed exactly as shown (rather than being an error) and should not be corrected. When found in a French document, (sic) stands for "Sans Intention Comique" (without comic intention) meaning that even if the preceding text could be understood as funny, it was not meant to be. It is used by writers quoting someone to alert the reader to the fact that an error or other weirdness in the quoted material is in the original, and not an error of transcription. "Sic" is almost always enclosed in parentheses.
A simple way to remember what it means is to consider sic as a pnemonic for 'spelt in context'.
1. I M (sic) and tired of literary shortcuts! - Used here to amplify that the shortcut "I M" is a shortcut used intentionally instead of "I am"
2. Not Here Today - I am il (sic).
3. Good grammer sic and spelling is sic important for writing good papers.