Udon noodles
Thick, soft Japanese wheat noodles with an elastic bite, usually served in broth or briefly stir-fried.
Udon is sold pre-cooked in vacuum packs, frozen, or dried in Asian grocery shops and increasingly in the Asian section of larger supermarkets. Frozen udon has the best springy, soft bite, while dried udon cooks up somewhat firmer and flatter.
Substitute:
Thick Chinese wheat noodles come closest; spaghetti or linguine will do in a broth at a pinch, but they are thinner and firmer, so the soft, elastic fullness of udon is lost.