knock for a loop


  1. a portion of a cord, ribbon, etc., folded or doubled upon itself so as to leave an opening between the parts.
  2. anything shaped more or less like a loop, as a line drawn on paper, a part of a letter, a part of a path, or a line of motion.
  3. a curved piece or a ring of metal, wood, or the like, used for the insertion of something, as a handle, etc.
  4. intrauterine device.
  5. Aeronautics. a maneuver executed by an airplane in such a manner that the airplane describes a closed curve in a vertical plane.
  6. a circular area at the end of a trolley line, railroad line, etc., where cars turn around.
  7. an arm of a cloverleaf where traffic may turn off or onto a main road or highway.
  8. Physics. the part of a vibrating string, column of air or other medium, etc., between two adjacent nodes.
  9. Electricity. a closed electric or magnetic circuit.
  10. Computers. the reiteration of a set of instructions in a routine or program.
  11. a wire, usually of platinum, one end of which is curved to form a loop, used for transferring microorganisms from one medium to another.
  12. a sand bar that encloses or nearly encloses a body of water.
  13. Figure Skating. a school figure in which a skater traces a large half circle, a small oval within its arc, and another large half circle to complete the figure while remaining on the same skating edge.
  14. the Loop, the main business district of Chicago.

verb (used with object)

  1. to form into a loop.
  2. to make a loop in.
  3. to enfold or encircle in or with something arranged in a loop.
  4. to fasten by forming into a loop, or by means of something formed into a loop (often followed by up): to loop up the new draperies.
  5. to cause (a missile or projectile) to trace a looping or looplike trajectory through the air: to loop a grenade into the building.
  6. to fly (an airplane) in a loop or series of loops.
  7. to construct a closed electric or magnetic circuit.
  8. Movies. to complete by means of looping: We still have to loop the final scenes.

verb (used without object)

  1. to make or form a loop: The river loops around the two counties.
  2. to move by forming loops, as a measuringworm.
  3. to trace a looping or looplike path through the air: The fly ball looped high in the air.
  4. to perform a loop or series of loops in an airplane.
  5. Movies. to record dialogue, sound effects, etc., onto an existing film track or soundtrack.
  1. in/out of the loop, included in or excluded from a group of people who receive the latest information about something: She’s often out of the loop on policy decisions.
  2. throw/knock for a loop, to astonish or upset: Her quitting the project really threw me for a loop.


  1. the round or oval shape formed by a line, string, etc, that curves around to cross itself
  2. any round or oval-shaped thing that is closed or nearly closed
  3. a piece of material, such as string, curved round and fastened to form a ring or handle for carrying by
  4. an intrauterine contraceptive device in the shape of a loop
  5. electronics
    1. a closed electric or magnetic circuit through which a signal can circulate
    2. short for loop aerial
  6. a flight manoeuvre in which an aircraft flies one complete circle in the vertical plane
  7. Also called: loop line mainly British a railway branch line which leaves the main line and rejoins it after a short distance
  8. maths physics a closed curve on a graphhysteresis loop
  9. another name for antinode
  10. anatomy
    1. the most common basic pattern of the human fingerprint, formed by several sharply rising U-shaped ridgesCompare arch 1 (def. 4b), whorl (def. 3)
    2. a bend in a tubular structure, such as the U-shaped curve in a kidney tubule (Henle’s loop or loop of Henle)
  11. computing a series of instructions in a program, performed repeatedly until some specified condition is satisfied
  12. skating a jump in which the skater takes off from a back outside edge, makes one, two, or three turns in the air, and lands on the same back outside edge
  13. a group of people to whom information is circulated (esp in the phrases in or out of the loop)


  1. (tr) to make a loop in or of (a line, string, etc)
  2. (tr) to fasten or encircle with a loop or something like a loop
  3. Also: loop the loop to cause (an aircraft) to perform a loop or (of an aircraft) to perform a loop
  4. (intr) to move in loops or in a path like a loop


  1. an archaic word for loophole

late 14c., “loop of cloth, rope, leather, etc.,” probably of Celtic origin (cf. Gaelic lub “bend,” Irish lubiam), influenced by or blended with Old Norse hlaup “a leap, run” (see leap (v.)). In reference to magnetic recording tape or film, first recorded 1931. Computer programming sense first attested 1947.


“to form a loop,” c.1400, “draw (a leash through a ring),” from loop (n.). Related: Looped; looping. Slang looped “drunk” is from 1934. Loop the loop (1900) originally was in reference to roller-coasters at amusement parks.

“Loop-the-Loop” is the name of a new entertainment which goes further in the way of tempting Providence than anything yet invented. The “Loop” is an immense circle of track in the air. A car on a mimic railway shoots down a very steep incline, and is impelled around the inner side of this loop. … The authorities at Coney Island are said to have prohibited “looping-the-loop” because women break their corset strings in their efforts to catch their breath as they sweep down the incline, and moreover, a young man is reported to have ruptured a blood vessel in his liver. [“Philadelphia Medical Journal,” Aug. 10, 1901]


  1. A curve or bend in a cord or other cylindrical body, forming an oval or circular ring.
  2. A type of loop-shaped intrauterine device.

Also, throw for a loop; knock down or over with a feather; knock sideways. Overcome with surprise or astonishment, as in The news of his death knocked me for a loop, or Being fired without any warning threw me for a loop, or Jane was knocked sideways when she found out she won. The first two of these hyperbolic colloquial usages, dating from the first half of the 1900s, allude to the comic-strip image of a person pushed hard enough to roll over in the shape of a loop. The third hyperbolic term, often put as You could have knocked me down with a feather, intimating that something so light as a feather could knock one down, dates from the early 1800s; the fourth was first recorded in 1925.

see in the loop; knock for a loop.

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