Making iTerm to translate 'meta-key' in the same way as in other OSes

Go to Bookmarks > Manage Profiles. Then select Keyboard Profiles > Global and choose Option Key as Meta. This works for me in version 0.9.6.1201.

1. Open "Preferences" (⌘,) -> Profiles -> Keys -> General tab.
2. Set Left Option key: to act as Esc+.

Works for me in Emacs, though I'm not sure if it will have any other undesirable effects.

In Menu bar Iterm2 => Preferences => Profiles choose the keys tab and select

left Option key act as +Esc

worked for me as well in irssi.