стремглав

Etymology
From via Russian Church Slavonic forms стрьмъглавъ, стремоглавъ, стремглавъ, which acquired modern meaning in 15th century, from  +  +.

Adverb

 * 1) precipitately, very fast, headlong
 * 2)  with the head down, headlong
 * 1)  with the head down, headlong