Definition of milk
It is also called "milking a player". When you "milk" a player, it means that you have a very strong hand and you are giving him a friendly price, a price that he can't refuse. I have if QQ on Q76Q8 and I bet 10% of the pot size on each street to make sure my opponent calls, I milk him. Milking is betting very little on each street instead of checking or betting standard, to maximize the size of the prize pool won.
Milk and metagame
If you are known as a player who likes to milk his opponents, you could try a metagame game. If you are playing against a player who knows you well and knows that you always have a very strong hand when you bet very small on the river, you could use this metagame to bluff him on the river by betting small, as if you had a very strong hand. If your bluff works, you can show him so that the next time he sees you bet small on the river, he won't be sure if you're bluffing cheap or milking it. It's an interesting metagame and you're swinging your range well.