header

noun

• 1 Soccer a shot or pass made with the head.

• 2 informal a headlong fall or dive.

• 3a brick or stone laid at right angles to the face of a wall. Compare with stretcher (sense 4).

• 4a line or block of text appearing at the top of each page of a book or document. Compare with footer¹ (sense 2).
• the part of an e-mail before the message, containing information such as the subject and sender:every e-mail message needs a header indicating the sender’s identity and addressCompare with body (sense 3 of the noun).

• 5 (also header tank) a raised tank of water maintaining pressure in a plumbing system.