Definition of "header"

header

/ˈhɛdɚ/

noun
plural headers
1. The upper portion of a page (or other) layout.
2. Text, or other visual information, used to mark off a quantity of text, often titling or summarizing it.
3. Text, or other visual information, that goes at the top of a column of information in a table.
4. (informal) A font, text style, or typesetting used for any of the above.
5. (computing) The first part of a file or record that describes its contents.
6. (programming) Clipping of header file.
7. (networking) the first part of a packet or stream, often containing its address and descriptors.
8. (masonry) A brick that is laid sideways at the top of a wall or within the brickwork with the short side showing.
9. A horizontal structural or finish piece over an opening.
10. A machine that separates and gathers the heads of grain etc.
11. (soccer) The act of hitting the ball with the head.
  Quotations
  The Black Cats had a mountain to climb after James Morrison's header and Shane Long's neat side-foot finish gave Albion a 2-0 lead five minutes in.
  2011 October 1, Phil Dawkes, “Sunderland 2 - 2 West Brom”, in BBC Sport‎
12. (soccer) Someone who heads the ball.
13. A headlong fall, jump or dive.
  Quotations
  "When the rest are in, you see one or two shiverin' on the bank, envyin' the others that have taken the plunge. It's the last that have the worst of it. I'm all for a header and have done with it."
  1913, Arthur Conan Doyle, “(please specify the page)”, in The Poison Belt […], London; New York, N.Y.: Hodder and Stoughton
14. A raised tank that supplies water at constant pressure, especially to a central heating and hot water system.
15. A pipe which connects several smaller pipes.
16. The rodeo performer who drives the steer toward the heeler to be tied.
17. One who puts a head on something.
verb
third-person singular simple present headers, present participle headering, simple past and past participle headered
1. (sports, transitive) To strike (a ball) with one's head.