Oxford Advanced American Dictionary

Definition of loop noun from the Oxford Advanced Learner's Dictionary

loop

noun
loop pronunciation English luːp loop pronunciation American luːp
 
1 a shape like a curve or circle made by a line curving right round and crossing itselfThe road went in a huge loop around the lake.Duclair is a small town on a loop of the River Seine.2 a piece of rope, wire, etc. in the shape of a curve or circleHe tied a loop of rope around his arm.Make a loop in the string.a belt loop (= on trousers/pants, etc. for holding a belt in place)3 a strip of film or tape on which the pictures and sound are repeated continuouslyThe film is on a loop. (figurative) His mind kept turning in an endless loop.4 (computing) a set of instructions that is repeated again and again until a particular condition is satisfied5 a complete circuit for electrical current6 (British English) a railway line or road that leaves the main track or road and then joins it again7 the Loop (US, informal) the business centre of the US city of Chicago
Idioms

in the loop

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out of the loop

(informal) part of a group of people that is dealing with something important; not part of this groupA lot of people want to be in the loop on this operation.Lawton had gradually been cut out of the loop on legal reviews.

knock/throw somebody for a loop

(North American English, informal) to shock or surprise somebodyThe result of the election knocked most people for a loop.