singlemost/single-most

[Archie]

I've heard this word several times, but what it really means still remains obscure to me.
Can you give me some synonyms and perhaps an example sentence using it?

 

[Tdol]

The number one, the max:
The singlemost important reason = it's by far the most important reason

 

[Archie]

Thank you very much tdol.
I 've consulted many dictionaries but I haven't managed to find this word.
Any idea why it's not included in dictionaries??

 

[Tdol]

You'll find it used, but dictionaries still prefer it as two words. ;-)