Nipple
noun, の adjective
What is a milk neck? Think about where milk comes from. Now, think of what looks like a little neck on the thing that milk comes from. What is that thing? It's a nipple.
The reading for this one is an exception, you already know that 首 is read as くび, but 乳 in this case is read as ち. Here's a mnemonic to help you.
You come across a nipple and decide to milk it so that you can make some cheese (ち). That's a little bit strange. You should probably find out who this nipple belongs to and ask them if you can do that first.
あそこで乳首にチクワを付けてダンスしてる人が私の上司です。
That man dancing over there with chikuwa on each of his nipples is my boss.
赤ちゃんにかまれて、乳首がカサブタだらけになってるんです。
My nipples are covered with scabs because the baby bites them.
あんたの乳首から血がふき出しているのを見て、思わずパニクッちゃったよ！
When I saw all the blood spurting out of your nipples, I couldn't help but panic!
哺乳瓶の乳首、熱湯消毒しておいたよ！
I've sterilized the feeding bottle nipples with boiling water.