noun
fish spear; leister; lance; trident
A multi-pronged spear used for fishing. やす is the common kana spelling; the kanji 簎 and 矠 are rare.
川でやすを使って魚を突いた。
I speared fish in the river using a fish spear.
夜、たいまつの明かりでやすを構える。
At night, I hold a fish spear ready by torchlight.
もり is a harpoon, often with a detachable head and a line, while やす is a fixed multi-pronged spear used for close-range fishing.
The origin is uncertain; it is a native Japanese word for a fishing tool.