from The American Heritage® Dictionary of the English Language, 4th Edition
- Contraction of cannot.
from Wiktionary, Creative Commons Attribution/Share-Alike License
- cannot; is unable to; does not have the ability to
- is forbidden to; is not permitted to
from the GNU version of the Collaborative International Dictionary of English
- A colloquial contraction for can not.
from The Century Dictionary and Cyclopedia
- A colloquial contraction of cannot.
can + -n't, since 1706 or earlier. (Wiktionary)