widthen

From width +‎ -en (verbal suffix).

widthen (third-person singular simple present widthens, present participle widthening, simple past and past participle widthened)

1. (transitive, intransitive, rare, nonstandard) To increase in width, or increase the width of; make or become wider or broader
   • 1984, Michael J. Harrison, Sidney A. Gauthreaux, Lilia A. Abron-Robinson, Proceedings, Wildlife Hazards to Aircraft Conference and Training Workshop:

     For the last few years this group has widthened its sphere of interest and is now called Communications and Flight Procedures Group.

   • 2016, Graeme Fowler, Absolutely Foxed:

     He used to hit the ball straight back, and as he batted over time his game, as he put it, 'widthened', until ultimately he could cut and pull.

• broaden
• widen

• breadthen

• windeth