godan verb (-tsu), intransitive verb
roll around in grass or mud
Describes an animal or person rolling about in grass, mud, or similar ground cover. Often used for animals such as dogs or horses.
犬が庭でぬたうっている。
The dog is rolling around in the garden.
馬が泥の中でぬたうつのが好きだ。
Horses like to roll around in the mud.
The exact derivation is uncertain. The word appears to be a compound of ぬた (mud, swampy ground) and うつ (to strike, hit), but the semantic shift to 'roll around' is not clearly documented.