It's actually *Meta*, emulated by an ESC character by the terminal. OSX tip: che...

akirk · on July 4, 2014

Which is fine if you never need to generate characters using the Option key. For example on a German keyboard you need the Option key to write { or }.

lloeki · on July 4, 2014

I'm on a french layout so I know :-)

It also has the side effect of "resurrecting" dead keys (which are unrelated to Option), making input of 'ê'and 'ï' impossible.

An alternative is using iTerm2 which has a similar setting, liberally applyable to either Option key.