1. 1. A solid piece of a hard substance, such as wood, having one or more flat sides.
   2. Such a piece used as a construction member or as a support.
   3. Such a piece upon which chopping or cutting is done: a butcher's block.
   4. Such a piece upon which persons are beheaded.
   5. One of a set of small wooden or plastic pieces, such as a cube, bar, or cylinder, used as a building toy.
   6. Printing. A large amount of text.
   7. Sports. A starting block.
2. A stand from which articles are displayed and sold at an auction: Many priceless antiques went on the block.
3. A mold or form on which an item is shaped or displayed: a hat block.
4. A substance, such as wood or stone, that has been prepared for engraving.
5. 1. A pulley or a system of pulleys set in a casing.
   2. An engine block.
6. A bloc.
7. A set of like items, such as shares of stock, sold or handled as a unit.
8. A group of four or more unseparated postage stamps forming a rectangle.
9. Canadian. A group of townships in an unsurveyed area.
10. 1. A usually rectangular section of a city or town bounded on each side by consecutive streets.
    2. A segment of a street bounded by consecutive cross streets and including its buildings and inhabitants.
11. A large building divided into separate units, such as apartments.
12. A length of railroad track controlled by signals.
13. The act of obstructing.
14. Something that obstructs; an obstacle.
15. 1. Sports. An act of bodily obstruction, as of a player or ball.
    2. Football. Legal interference with an opposing player to clear the path of the ball carrier.
16. Medicine. Interruption or obstruction of a physiological function: nerve block.
17. Psychology. A sudden cessation of speech or a thought process without an immediate observable cause, sometimes considered a consequence of repression. Also called mental block.
18. Slang. The human head: threatened to knock my block off.
19. A blockhead.

1. To shape into a block or blocks.
2. To support, strengthen, or retain in place by means of a block.
3. To shape, mold, or form with or on a block: block a hat.
4. 1. To stop or impede the passage of or movement through; obstruct: block traffic.
   2. To shut out from view: a curtain blocking the stage.
   3. To stop the passage of (a motion or bill) in a legislative assembly.
5. To indicate broadly without great detail; sketch. Often used with out: block out a plan of action; block out stage movements.
6. Sports. To impede the movement of (an opponent or the ball) by physical interference.
7. Medicine. To interrupt or obstruct the proper functioning of (a physiological process), especially by the use of drugs.
8. Psychology. To fail to remember.
9. To run (trains) on a block system.

1. Sports. To obstruct the movement of an opponent.
2. To suffer a mental block. Often used with on: I blocked on his name.

block out

1. To cover over so as to be illegible: block out sensitive information from a document before releasing it.
2. To repress (a traumatic event, for example) from conscious memory.

go on the block

1. To be offered for sale.

1. From a starting position, as in a race or contest: The company has in the past been slow out of the blocks to adapt to consumer tastes.

1. To offer for sale.

[Middle English blok, from Old French bloc, from Middle Dutch.]

SYNONYMS   block, hide, obscure, obstruct, screen, shroud. These verbs mean to cut off from sight: a tree that blocked the view; a road hidden by brush; mist that obscured the mountain peak; skyscrapers obstructing the sky; a fence that screens the alley; a face shrouded by a heavy veil. See also synonyms at hinder¹, obstacle.

The American Heritage® Dictionary of the English Language, Fourth Edition Copyright © 2007, 2000 by Houghton Mifflin Company. Updated in 2009. Published by Houghton Mifflin Company. All rights reserved.