spiral
Pronunciation: /ˈspʌɪr(ə)l/
adjective
- winding in a continuous and gradually widening (or tightening) curve, either around a central point on a flat plane or about an axis so as to form a cone: a spiral pattern
- winding in a continuous curve of constant diameter about a central axis, as though along a cylinder; helical.
- (of a stairway) constantly turning in one direction as it rises, around a solid or open centre: a wrought-iron spiral staircase
- Medicine (of a fracture) curving round a long bone lengthwise.
- short for spiral-bound. a spiral notebook
noun
- 1a spiral curve, shape, pattern, or object: a spiral of smoke
- Astronomyshort for spiral galaxy.
- 2a progressive rise or fall of prices, wages, etc., each responding to an upward or downward stimulus provided by a previous one: an inflationary spiral
- a process of deterioration through the continuous increase or decrease of a specified feature: this spiral of deprivation and environmental degradation
verb ( spirals, spiralling, spiralled; US spirals, spiraling, spiraled)

Origin:
mid 16th century (as an adjective): from medieval Latin spiralis, from Latin spira 'coil' (see spire2)

Spelling rule
Double the l when adding endings which begin with a vowel to words which end in a vowel plus l (as in travel):