It depends on how you want it to react.... one option is to remove the css:
ul#cssmw li {menu.css (line 18)
white-space:nowrap;
removing the white-space attribute would allow the text to go to the next line.
The other option is to update the css:
ul#cssmw ul.level-1 > li > span > a
and remove the width attribute. This will allow the column to stretch to fit the text and it won't have to wrap.
Either solution should work depending on the result you expect.