1. hold stubbornly to a position, work energetically
dig your heels in and refuse to budge
Dig in is a phrasal verb with a number of meanings. To dig in can mean to start eating enthusiastically so if you present a meal to your friends, to invite them to start eating- you can say, 'please dig in!'. To dig into something can also mean to press hard into something else, for example, 'I was so angry I dug my nails into the palm of my hands to stop from shouting'. You can also dig into the ground or mix something into the ground using a shovel. 'Settlers on the island used to dig in seaweed to fertilise the soil'. To dig in for means to prepare yourself for something difficult which is coming. For example, 'I dug in for a long custody battle over the children'. In a battle or war situation soldiers can dig in or dig themselves into trenches in order to prepare for an attack.