Yes, header is a Scrabble word!

Noun

1. A line of text serving to indicate what the passage below it is about

2. Horizontal beam used as a finishing piece over a door or window

3. Brick that is laid sideways at the top of a wall

4. A framing member crossing and supporting the ends of joists, studs, or rafters so as to transfer their weight to parallel joists, studs, or rafters

5. A machine that cuts the heads off grain and moves them into a wagon

6. (soccer) the act of hitting the ball with your head

7. A headlong jump (or fall)