noun
millipede
A common terrestrial arthropod with many legs; often found in damp places.
庭の石の下にヤスデがいた。
There was a millipede under the stone in the garden.
ムカデ (centipede) is a different arthropod with one pair of legs per segment, often faster and sometimes venomous, while ヤスデ has two pairs per segment and is harmless.
The origin is uncertain; the kanji 馬陸 literally means 'horse land', but this is likely an ateji assignment based on Chinese usage.