An onomatopoeic word for a high, whistling or whizzing sound (e.g., wind or something flying past). Often used with the particle 'to'.
冬の夜、窓の隙間を風がヒューと吹き抜けた。
On a winter night, the wind whistled through the gap in the window.
ボールが頭の上をヒューッと飛んで行った。
The ball whizzed over my head.
観客がヒューと口笛を吹いた。
The audience let out a whistle (a 'hue' sound).