The giant spider, s, is a monster in NetHack. They are faster than you and have a rather damaging poisonous bite; however, they are too large to be able to hide as some of their kin are capable of. Their corpses are poisonous.
If you are polymorphed into a giant spider, you can spin Webs using the #monster command without using up any power. Spinning a web inside of a monster with a digestion attack will cause it to spit you out (webs do not bother other engulfers). Spinning a web can be used to remove a (spiked) pit, hole, trap door, or rolling boulder trap. This is done without creating a web on the same square that must be removed. Since most other traps can be removed by digging a pit over them, it is possible to permanently remove almost any trap.
A giant spider is generated every time a spider web trap is randomly generated.
Encyclopedia entry Edit
Eight legged creature capable of spinning webs to trap prey.
"You mean you eat flies?" gasped Wilbur.
"Certainly. Flies, bugs, grasshoppers, choice beetles,
moths, butterflies, tasty cockroaches, gnats, midges, daddy
longlegs, centipedes, mosquitoes, crickets - anything that is
careless enough to get caught in my web. I have to live,
"Why, yes, of course," said Wilbur.