kid 
(kĭd)
(kĭd)n.
1.
a. A young goat.
b. One of the young of certain similar animals.
2.
a. The flesh of a young goat.
b. Leather made from the skin of a young goat; kidskin.
c. An article made from this leather.
3. Informal
a. A child.
b. A young person.
4. Slang Pal. Used as a term of familiar address, especially for a young person: Hi, kid! What's up?
adj.
1. Made of the skin or with the meat of a young goat.
2. Informal Younger than oneself: my kid brother.
v. kid·ded, kid·ding, kids
v.tr.
1. To mock playfully; tease: They kidded me about my mismatched socks.
2. To deceive in fun; fool: I could only hope they were kidding me when they said my car had been stolen.
3. To deceive (oneself), especially by allowing one's desires to cloud one's judgment: You're kidding yourself if you think that plan will work.
v.intr.
Idiom: 1. To engage in teasing or good-humored fooling: You want that much for your old car? You must be kidding!
2. To bear young. Used of a goat or similar animal.
no kidding
1. Used to express surprise or disbelief.
2. Used to express scornful acknowledgment of the obvious.
[Middle English kide, from Old Norse kidh.]
kidder n.
kidding·ly adv.