The Proto-Turkic word *bus
Word *bus
Meaning steam, fog

Comments
S. A. Starostin, A. V. Dybo, O. A. Mudrak - An Etymological Dictionary of Altaic Languages, 2003, Brill

Other words that might be of interest
*bulut ‘cloud’, *āń(k) ‘moon, month’, *jul-du-ŕ ‘star’, *gün(eĺ) / guńaĺ ‘sun, day, sunny place, sun-heat’, teŋri ‘god, sky, heaven’