interj.
Pronunciation: often read as ' hwü, ' wü, ' hyü; the interj is a whistle concluded with a voiceless ü
Function: noun
Etymology: imitative
Date: 1513
: a whistling sound or a sound like a half-formed whistle uttered as an exclamation <gave a long whew when he realized the size of the job> ― used interjectionally chiefly to express amazement, discomfort, or relief