Accidentally typing a message in the wrong window on the computer - eg using instant messenger chat, IRC, or even a word processor.
Shortened form of "sent to the wrong window".
davis> Yeah, she's awesome hey..
tormsen> Talked to her recently?
carlo> /download LESBIAN_PORN -all
carlo> oops. miswindow.
Free Daily Email
Emails are sent from email@example.com. We'll never spam you.