When an educated person makes a common synonym error, such as switching they're for their, due to a cognitive mistake and not their ignorance of grammar.
Gentlemanly Scholar: I just finished making a finely worded point and your foolish.
Other Guy: you're*
Gentlemanly Scholar: Sorry dog, that was a synowhim.
Other Guy: you're*
Gentlemanly Scholar: Sorry dog, that was a synowhim.
by Ericofgreatepithet October 21, 2012
Get the Synowhimmug.