noun
plain udon noodles; udon without toppings
Refers to udon served in hot broth without any toppings, as opposed to 掛けうどん which may include toppings. A simple, basic style of udon.
See also: 掛けうどん
寒い日は素うどんが食べたくなる。
On cold days, I crave plain udon noodles.
素うどんに天かすを入れると美味しい。
Adding tempura bits to plain udon makes it delicious.
掛けうどん is udon with toppings or a specific style, while 素うどん is plain udon without trimmings.
素 (plain) + うどん (udon noodles). The exact historical derivation is uncertain, but the term straightforwardly describes udon served without additional toppings.