How To Spell Submachine

What is the correct way to write submachine gun? Is it:

1. submachine gun
2. sub machine gun
or
3. sub-machine gun?

I always thought it was 1, but I can't find submachine in any dictionary.

 

Merriam-Webster says your gut was right.

 

Wikipedia uses the first spelling. Also doesn't 'look' weird to me.

 

Thanks. Libre Office spell check keeps telling me I'm wrong.

 

I use libreoffice too and its spellcheck gives me endless grief, hahah. I feel you.

 

I was looking at switching to LibreOffice, but this is one of the reasons I didn't. Who's got time to fix their dictionary?

Also, the default way to start any programme in LO is through that silly all-in-one window. Not a fan.

 

(Quietly opens Google Docs and relishes in slightly superior spell-check system)