An external respiratory opening, especially each of a number of pores on the body of an insect, or each of a pair of vestigial gill slits behind the eye of a cartilaginous fish.
- ‘Catsharks have moderately large spiracles, or respiratory openings, and five pairs of gill slits.’
- ‘Its spiracles located behind the eyes allow the guitarfish to remain under the sand for long periods of time and breathe easily by flushing clean water over the gills.’
- ‘It has long been suggested that insects close the spiracles to prevent desiccation, minimizing water loss but exposing themselves to hypoxic stress.’
- ‘There is a hole called a spiracle behind each eye.’
- ‘Insects ‘breathe’ through a tracheal system, with external openings called spiracles and increasingly finely branched tubules that carry gases right to the metabolizing tissues.’
Late 18th century: from Latin spiraculum, from spirare breathe.