a weakened version of "fuck!" or "fucking hell!". to be used in times of massive frustration. you know, the kind that sucks all your energy at lightening speed so as to render you unable to truly let loose on someone's ass for crossing you like they just did. eh, or as a substitute for the aforementioned, more graphic, vocabulary when you are in the company of minors but just can't stop from swearing - oh, and can be used in exclamation, normal tone, or a whisper (just as versatile as the original in that sense).
using a milder, yet exacerbated tone:
"I'm still at work. I am stuck. I have stuff to do and I'm stuck. Feh." Less genteel possibilities can be found by hanging around bars, college parties, or high school cafeterias.