What is "to dig in one's heels"

Dig \Dig\ (d[i^]g), v. t. [imp. & p. p. Dug (d[u^]g) or Digged (d[i^]gd); p. pr. & vb. n. Digging. -- Digged is archaic.] [OE. diggen, perh. the same word as diken, dichen (see Dike, Ditch); cf. Dan. dige to dig, dige a ditch; or (?) akin to E. 1st dag. [root]67.]

1. To turn up, or delve in, (earth) with a spade or a hoe; to open, loosen, or break up (the soil) with a spade, or other sharp instrument; to pierce, open, or loosen, as if with a spade.

   Be first to dig the ground.
   --Dryden.

2. To get by digging; as, to dig potatoes, or gold.

3. To hollow out, as a well; to form, as a ditch, by removing earth; to excavate; as, to dig a ditch or a well.

4. To thrust; to poke. [Colloq.]

   You should have seen children . . . dig and push their mothers under the sides, saying thus to them: Look, mother, how great a lubber doth yet wear pearls.
   --Robynson (More's Utopia).

5. To like; enjoy; admire. The whole class digs Pearl Jam. To dig down, to undermine and cause to fall by digging; as, to dig down a wall. To dig from, To dig out of, To dig out, To dig up, to get out or obtain by digging; as, to dig coal from or out of a mine; to dig out fossils; to dig up a tree. The preposition is often omitted; as, the men are digging coal, digging iron ore, digging potatoes. To dig in,

   1. to cover by digging; as, to dig in manure.

   2. To entrench oneself so as to give stronger resistance; -- used of warfare or negotiating situations.

      to dig in one's heels To offer stubborn resistance.