dig in

verb5

1. •
   To dig trenches to resist an enemy attack.

   • If Russia choses to dig in, then the military balance – which typically favours the defender on a 3-1 ratio – is reversed. — 2022
2. •
   (informal) To begin eating.

   • I wanted to say grace before dinner, but the kids were already digging in.
3. •
   To adopt a resolute state of mind.

   • to dig in one's feet, heels, etc.
4. •
   (informal) To engage in a burst of hard work.

   • I've got to dig in for a couple of weeks to secure my promotion.
5. •
   To cover over by digging.