WC stands for Weapon Class; it's basically the damage you can do per hit.
How it works
If an item has say, 25 WC, then it may do an average(or max?) of 25 damage per hit. However, if it has two different WCs, then it may do one OR the other. For example: Hunter's Claws has 35 Stab WC and 30 Smash WC; but, instead of stacking and doing both 35 Stab and 30 Smash WC, it might do 35 Stab damage OR 30 Smash damage. I speculate that this is chosen at random per every attack.