I have seen it couple of times in a chat room on the internet. What does "insteadly" mean? Is it a shortcut of "instead of"?
"Insteadly" is not a standard English word. As others have noted, it appears to be a typo for instantly.
I would think this is probably due the pronunciation of [ˈɪnstəntli] as [ˈɪnstədli] in quick speech, where the hearer has not seen the word spelled before.
EDITED TO ADD: After a Google perusal I see only three usages:
- This post.
- Non-native English speakers using it in place of "instantly".
- Non-native English speaker using it in place of "instead".