loop has 11 distinct synonyms spread across 7 of its 15 senses. Each sense below keeps its own list, because a synonym belongs to a meaning and not to a word: swapping one sense's substitute into another sense's sentence is how a thesaurus makes writing worse. WordNet records no antonym for it — antonymy is a relation between word forms rather than concepts, so it is deliberately sparse.
Counts are distinct word forms across every sense. A synonym that appears under three senses is counted once here and shown three times below, under each sense it belongs to.
an inner circle of advisors (especially under President Reagan)
“he's no longer in the loop”
the basic pattern of the human fingerprint
a computer program that performs a series of instructions repeatedly until some specified condition is satisfied
the topology of a network whose components are serially connected in such a way that the last component is connected to the first component
an intrauterine device in the shape of a loop
a complete electrical circuit around which current flows or a signal circulates
a flight maneuver; aircraft flies a complete circle in the vertical plane
move in loops
“The bicycle looped around the tree”
Synonyms, antonyms and the broader and narrower relations for loop come from Princeton University’s WordNet. Full sources and licences.
fly loops, perform a loop
“the stunt pilot looped his plane”
fasten or join with a loop
“He looped the watch through his belt”