snail

noun

1. Any of very many animals (either hermaphroditic or nonhermaphroditic), of the class Gastropoda, having a coiled shell.

   “‘Children crawled over each other like little grey worms in the gutters,’ he said. ‘The only red things about them were their buttocks and they were raw. Their faces looked as if snails had slimed on them and their mothers were like great sick beasts whose byres had never been cleared. […]’”

2. (broadly, informal)A slow person; a sluggard.
3. A spiral cam, or a flat piece of metal of spirally curved outline, used for giving motion to, or changing the position of, another part, as the hammer tail of a striking clock.
4. (historical)A tortoise or testudo; a movable roof or shed to protect besiegers.
5. The pod of the snail clover.
6. A locomotive with a prime mover but no traction motors, used to provide extra electrical power to another locomotive.

verb

1. To move or travel very slowly.

   “The cars were snailing along the motorway during the rush hour.”